The document contains revision questions about corrosion and surface preparation. It discusses topics like corrosion circuits, factors that influence corrosion, electrolytes, types of surface finishes, and methods of surface preparation like blasting and cleaning. Various terms related to surface preparation are defined, like millscale, hackles, and profiles. Assessment methods for surface finishes are also addressed.

1. Revision Questions
1. Is the electrical circuit in a corrosion reaction AC or DC?
Ans. DC.
2. Does corrosion occur at the cathode or at the anode?
Ans. Anode.
3. Name the three factors needed for corrosion to occur.
Ans. Anode, Cathode and Electrolyte.
4. What is meant by the term electrolyte?
Ans. A substance, which will conduct current and be broken down.
5. What is corrosion?
Ans. Degradation of a material by chemical or electrochemical means.
6. In the corrosion circuit do electrons flow from anode to cathode?
Ans. Yes, electrons flow from anode to cathode via metallic path.
7. Which gas is released at the cathode when the electrolyte is water?
Ans. Hydrogen (H₂).
8. Which is the more noble metal, steel or aluminium?
Ans. Steel.
9. Which is more electronegative, steel or aluminium?
Ans. Aluminium.
10. If steel and copper were in contact in an electrolyte which would corrode?
Ans. Steel.
11. Name two common hygroscopic salts.
Ans. Iron Sulphates & Iron Chlorides.
12. Name three metals used as sacrificial anodes on a steel pipeline
Ans. Zinc, Aluminium & Magnesium.
13. What is the approximate thickness of millscale?
Ans. From 25 to 100 Microns.

2. 14. Which of the two metals would corrode if steel and zinc were coupled?
Ans. Zinc.
15. Which other names relate to the Galvanic List?
Ans. Electromotive Forces Series, Electrochemical Series.
16. In which environment are you likely to encounter chloride salts?
Ans. Marine Environment.
17. Which three compounds together form millscale?
Ans. Haematite, Wusatite & Magnetite.
18. If magnesium was coupled with zinc, which would corrode?
Ans. Magnesium.
19. In which environment would sulphate salts be found?
Ans. Industrial (Power Stations etc.) and Agricultural Areas.
20. What is an osmotic blister?
Ans. Tiny, pinhead- sized, water- blisters caused by Hygroscopic salt contamination. (Iron Sulphates/
Iron Chlorides).
21. What is an ion?
Ans. A positively or negatively charged particle or atom. UNSTABLE ATOM.
22. What is meant by polarisation?
Ans. The polarity (Positive or Negative) of an atom.
23. Is an anode positive or negative?
Ans. Positive.
24. Can corrosion occur without an electrolyte?
Ans. NO.
25. Name a sub atomic particle.
Ans. Proton, Neutron and Electron.
26. What is millscale and when and where does it occur?
Ans. Millscale is a thin flaky layer of iron oxides formed and compressed during rolling operation of
steel section RSA, RSC & RSJ when temperature is above 580° C. The oxides formed are
Haematite, Wusatite and Magnetite.The colour of mill scale is 25- 100 µm.

3. 27. Name three factors, which can accelerate corrosion reactions.
Ans. Temperature, Bacteria, Hygroscopic Salts, Acid & Alkalis, Bi- metallic corrosion (galvanic list
location) and Aerobic Conditions.
28. Why is it considered essential to remove millscale prior to painting?
Ans. It prevents Bi- metallic corrosion (mill-scale is more noble than the steel) and improves
adhesion & cleanliness.
29. Why does an un-coated steel plate corrode?
Ans. Steel is heterogeneous, as it exists as both a cathode and an anode simultaneously. Electrons
enter at every available point of the substrate. Iron reacts readily with oxygen to form iron oxide
(rust).
30. If corrosion occurs at anodic areas, why does steel corrode evenly all over the surface?
Ans. Trace alloying elements in the steel (Nickel, Carbon, Aluminium etc.) provides millions of anodic
and cathodic areas, (Bi- metallic contact) so thesteel surface will corrode (as it is both an anode
and a cathode).

4. 1. Which British standard would be used in determining the size of copper slag abrasive?
Ans. BS 410.
2. Which British standard would be used in determining the size of metallic abrasives?
Ans. BS 410.
3. Which regulations prohibit the use of sand for blasting steel?
Ans. COSHH (MSDS or data Sheets) & 1657.
4. What is meant by the term ‘key’?
Ans. The cross section of blasted area as measured from the top of the peak to the bottom of the
trough is called peak or surface profile.
5. Why is it important to have good surface preparation?
Ans. To improve adhesion and remove contamination which gives a surface profile of 10 years life as
expected.
6. What is meant by the term sliver?
Ans. It is the lamination that appears to be a longitudinal crack. It is a surface breaking lamination.
7. What is a hackle?
Ans. A small surface lamination, which stands upright like a needle after blasting. Approximately ≤
13 mm. Easily removed.
8. Name two other terms that could be used for anchor pattern?
Ans. Peak to Trough, key, surface profile, amplitude.
9. What are the main advantages of using Testex papers for measuring profiles?
Ans. It proved a permanent record and it can be used on curved surfaces.
10. What is meant by the term grade, relating to a blast finish?
Ans. Degree of surface cleanliness.
11. What are the main factors governing the grade of a blast finish?
Ans. Time spent, abrasive size, abrasive density, material density, shape of particles, hardness of the
abrasive, initial rust grade.
12. Can the grade of a blast finish be determined by using the surface comparators to BS 7079 Pt
C3?
Ans. No, only surface roughness.

5. 13. What profile range can be measured using ‘X coarse’ Testex?
Ans. 37- 115 µm.
14. What profile range can be measured using ‘coarse’ grade Testex?
Ans. 20- 50 µm.
15. What are the two theories of adhesion?
Ans. Molecular Interference and Molecular Adhesion.
16. Briefly describe the mechanisms of the two theories of adhesion.
Ans. (i)Molecular interference: - Because surface rough and uneven paint gets lock and wet the
profile.
(ii)Molecular Attraction: - Charged particles are attracted to each other, negative to positive and
vise versa.
17. How many microns are in 1thou?
Ans. 25.4
18. Give three different names for the cross section of a blast.
Ans. Surface Profile, Anchor Pattern, Key, Peak to Trough, Amplitude.
19. What is the approximate speed of abrasives leaving a venturi nozzle?
Ans. 450 mph.
20. What is the most common cause of flash rusting on a blasted substrate?
Ans. Moisture.
21. What would be considered to be an ideal shot grit mix?
Ans. 70- 80% shot/ 20- 30% grit.
22. What is the purpose of mixing shot and grit?
Ans. Grit cuts the profile & shot controls the peaks, to give a uniform profile.
23. Which abrasive would have the effect of work hardening a substrate?
Ans. Metallic shot or steel shot.
24. Name three methods of measuring or assessing a profile.
Ans. Comparators, Visual, Touch (tactile), Surface Profile Needle Gauge, Dial Micrometer & Replica
Tape.
25. What is the most common cause of rogue peaks on a substrate?

6. Ans. Concentrated blasting in one area for too long.
26. In what situation would it be better to use steel grit in preference to copper slag abrasives?
Ans. Enclosed Blast Cabinets or Wheelabrators.
27. If cracks or laminations are found on a substrate after blasting what steps should be taken?
Ans. Stop the blasting operation, mark the area and report it to the site engineer (Ultrasonic
lamination checks normally follow).
28. Using comparators to ISO 8503, what are the three main profile assessments?
Ans. Fine, Medium and Coarse.
29. What are the other two assessments when the above three are not appropriate?
Ans. Finer than fine and coarser than coarse.
30. What would be size of copper slag needed to give a profile of 50 to 75µm?
Ans. G16 (J Blast Supa is most common).

7. Surface preparation
1. What is the title of the BS 7079?
Ans. Preparation of steel substrates before application of paints and related products.
2. What are the four characteristics of an abrasive?
Ans. Size, hardness, density, shape.
3. Why are blast hoses carbon impregnated?
Ans. Static electricity discharge.
4. Name the gauge used for measuring pressure at the blast nozzle?
Ans. Hypodermic Needle Gauge.
5. Name four advantages of centrifugal blasting over open blasting.
Ans. Recycleable abrasives, operator safety, quality control, no operator fatigue.
6. According to BS 7079 is it possible to blast clean to an A Sa1?
Ans. No.
7. Is there any difference between an A Sa1 and B Sa1?
Ans. Yes.
8. Could you tell the difference between rust grades A and B blasted to Sa3?
Ans. No.
9. Could you tell the difference between rust grades C and D blasted to Sa3?
Ans. Yes, possible heavy pitting.
10. What would be a typical speed of abrasives leaving a wheel abrator?
Ans. 220 mph.
11. What is considered to be the most efficient blasting pressure?
Ans.100 psi.
12. What is meant by the term burnishing?
Polishing or shining of the material surface.
13. What would be the equivalent to St2 in the Sa grades?
Ans. Sa 2½.
14. What is the neutral figure on the pH scale?

8. Ans. Seven(7).
15. What is the meaning of pH, and how is it measured?
Ans. Potential Hydrogen (level of acidity or alkalinity) using a litmus paper or pH indicators
16. Why are inhibitors sometimes added to water in wet blasting?
Ans. To prevent flash rusting (immediate oxidation).
17. Name two typical areas where needle guns might be used?
Ans. Rivets, bolts, weld cap profile, plate overlap.
18. What is the duplex process of surface preparation?
Ans. Pickling followed by passivation (Footners- Duplex System).
19. Which pH range covers acid, and which range covers alkalis?
Ans. 0 to 7 acids, 7 to 14 alkalines.
20. Name two areas on a structure where flame cleaning cannot be done.
Ans. Areas of fastening under tension (bolts, rivets, screws etc.).
21. Which three basic operations are performed during flame cleaning?
Ans. Expansion, Dehydration, Heat Penetration.
22. How does BS 7079 define flame cleaning standards?
Ans. AFL, BFL, CFL and DFL.
23. What is a Jason’s Hammer?
Ans. A pneumatic caulking chisel, a type of needle gauge.
24. What is meant by St2 and St3?
Ans. Through hand and power tool cleaning, Very through hand and power tool cleaning.
25. Two alloys are used to render wire brushes spark free, what are they?
Ans. Phosphor Bronze/ Beryllium Bronze.
26. Why should burnishing be avoided?
Ans. Polished surfaces give poor adhesion.
27. Name two major disadvantages of using a needle gun.
Ans. Work hardening, operator fatigue, very coarse surface profile, Health and safety issuedue to
vibration white finger.

9. 28. After phosphating, what would be a typical pH requirement prior to coating?
Ans. 4.5 to 7.0.
29. What is understood by the term knock out pot?
Ans. A small vessel with a drain tap, to remove oil and water vapour from the compressed air
stream.
30. If an operator was blasting with a nozzle pressure of 80 psi. What would be his approximate
efficiency?
Ans. 70% (80 psi = 20 x 1.5 efficiency drop = 30%).
31. Which solvents are commonly used for degreasing?
Ans. Xylene.
32. What is a ‘dead mans handle’?
Ans. Safety Cut- Off Trigger controlling the abrasive stream, which must be under the direct control
of the blasting operator.
33. How is abrasive cleansed in a wheel abrator system?
Ans. Air wash separator.
34. What is the main disadvantage of high pressure jetting compared to other systems?
Ans. Lack of safety, huge volume of water, slurry, no profile, flash rusting.
35. Name five methods of wet blasting.
Ans. (i) Steam.
(ii) Air blasting plus water.
(iii) High pressure.
(iv) High pressure plus abrasives.
(v) Low pressure plus abrasives.
36. What are the typical temperatures and concentration of sulphuric acid in the pickling process?
Ans. 5-10% at 65° to 70°.
37. Describe the duplex process.
Ans. Degrease using xylene. Check with Ultraviolet light. Immerse in 5-10% sulphuric acid for 5-25
mins at 65-70 degrees C. rinse with clean warm water. Immerse in 1-2% Phosphoric or Chromic
acid, at 80° C for 1-2 mins, with addition of 0.5% iron fillings. Rinse with clean warm water.
Check pH level, to be between 4.5 to 7.0.
38. What would be a maximum pressure for high pressure water jetting?
Ans. 30,000 psi (above this is said to be Ultra High Pressure).

10. 39. What are the disadvantages of wet blasting over dry blasting?
Ans. Cuts no profile, large amounts of slurry, large volume of water, flash rusting.
40. What would be considered to be advantages of wet blasting over dry blasting?
Ans. Sprak free operation, removal of toxic detritus, removes Hygroscopic salts.
41. Why is the phosphating or chromating of steel done?
Ans. Give limited protection against corrosion & help to prevent flash rusting.
42. What would be an acceptable remedy for burnished areas?
Ans. Emery cloth & emery paper.
43. Would burnishing be expected on areas of St2 preparation?
Ans. No.
44. How many photographs of blast cleaning standards are shown in BS 7079 Pt A?
Ans.14 (blast cleaning standards).
45. Do the plates shown in BS 7079 Pt A relate to grit blasting or shot blasting?
Ans. It refers to all types of blasting.

11. Paint technology (1)
1. Name a third type of paint other than solvent free and solvent borne.
Ans. Powder.
2. An epoxy resin would use which solvent?
Ans. Acetone.
3. Name four or more advantages of chlorinated rubber paints.
Ans. Durability, flameproof, resistant to algae/ mould growth, not reliant upon surface profile,
waterproof.
4. What are the three main disadvantages of chlorinated rubber paint?
Ans. Poor resistance to HC solvents, can not be made water- bourne, low temperature tolerance.
5. Which solvent could be used with a phenolic resin?
Ans. White spirit.
6. Chlorinated rubber paint would contain which solvent?
Ans. Xylene.
7. Would it be good practice to apply chlorinated rubber over alkyd resin?
Ans. No.
8. Which solvent would be used with an alkyd resin?
Ans. White spirit.
9. How was the word alkyd derived?
Ans. It is derived from an Alcohol/ Acid reaction.
10. What is meant by opaque?
Ans. Hiding or covering power. The ability to hide underlying layer.
11. What is meant by vehicle?
Ans. Binder, film former, Non- Volatile.
12. Would it be acceptable practice to apply an alkyd over chlorinated rubber?
Ans. Yes.
13. Would it be acceptable practice to apply chlorinated rubber over phenolic?
Ans. No.

12. 14. Would it be acceptable practice to apply phenolic resin over chlorinated rubber?
Ans. Yes.
15. Would it be acceptable practice to apply epoxy over linseed oil base?
Ans. No.
16. Would it be acceptable practice to apply chlorinated rubber over epoxy?
Ans. Yes.
17. Would it be acceptable practice to apply epoxy resin over alkyd resin?
Ans. No.
18. What is another name for an un-pigmented paint?
Ans. Varnish or lacquer.
19. What are the natural properties of a resin?
Ans. Brittle and fast drying.
20. What are the natural properties of an oil?
Ans. Slow drying and elastic.
21. How does paint using the barrier principle work?
Ans. Physically prevents the electrolyte from making contact with the substrate.
22. How does paint using the passivation principle work?
Ans. Phosphate and Chromate react with iron, to create a layer of rust inhibitive ‘passivating’ salts.
23. How does paint using cathodic protection principle work?
Ans. By incorporating a metallic pigment of lower nobility than the steelinto the paint (zinc &
aluminium).
24. Give another name for solvent free two packs.
Ans. Multi- Component Liquid or ‘MCL’.
25. Name six properties of a binder.
Ans. Resistance to: abrasion/ acid & alkaline/ water/ electrons, keep the pigments in suspension,
cohesive/ adhesive strength/ change from liquid into a solid.
26. Name three natural resins used in paints.
Ans. Copals, Dammars, Coumaroness, Amber, Laq.
27. Name five natural oils used in paints.

13. Ans. Olive, Linseed, Palm, Castor, Coconut, Soya.
28. What does oleoresinous mean?
Ans. A mixture of oil and resin.
29. Name an Inorganic high temperature service binder.
Ans. Silicates & silicones.
30. Name two pigments likely to be used for high temperature service.
Ans. Zinc and Aluminium.

14. Paint technology (2)
1. By what name would you call the basic unit of a polymer?
Ans. Mer, Molecule, Atom.
2. What is polymerisation?
Ans. The joining together of a string or structure of repeated units.
3. Name three types of polymers.
Ans. Linear, Branched, Crosslinked.
4. What would be the characteristics of a short oil paint?
Ans. Less than 45% Oil to Resin, faster drying, suitable for steel work.
5. What would be the characteristics of a long oil paint?
Ans. More than 60% Oil to Resin, slower drying, mainly decorative applications.
6. What is meant by the term opaque pigment?
Ans. Pigment with excellent “light scattering” properties, or “hiding ability”. It is said to have
“covering power”.
7. What is a typical size of a pigment particle?
Ans. 0.1 to 1.0 microns.
8. Briefly describe the difference between saturated and unsaturated when referring to oils or
polymers.
Ans. Unsaturated oils will react with oxygen and solidify, saturated oils will not, so they are classed
as non- drying oils.
9. Name two drying oils, which are unsaturated.
Ans. Llinseed, Tung, Soya, Safflower, China Wood.
10. What is the main difference between a dye and a pigment?
Ans. A pigment must reamin solid within binder. (A dye will dissolve)
11. What are the sources of pigments?
Ans. Anmal, Mineral, Synthetic, Vegetable.
12. If titanium dioxide was used in paint, what would be the colour?
Ans. White.
13. Name three rust inhibitive pigments considered to be toxic.
Ans. Red Lead, Coal Tar, Calcium Plumbate, Zinc Chromate, Zinc Phosphate.

15. 14. Name four commonly occurring minerals used as extender pigments.
Ans. Talc, Chalk, Slate Flour, China Clay.
15. Name three laminar pigments.
Ans. MIO, Mica, Glass Flake, Graphite.
16. If pigment was added way below the CPVC, how would it affect the film?
Ans. Low opacity, Blistering, Low Cohesive Strength, High Gloss.
17. The abbreviation CPVC means what?
Ans. Critical Pigmaent Volume Concentration.
18. Why are thixotropes added to a paint formulation?
Ans. Anti- Settling agent, Thickener, Storage aid.
19. If carbon was used as a pigment what would be the paint colour?
Ans. Black
20. Name four properties that a binder contributes to a paint film.
Ans. Adhesion, ease of application, cohesive strength, Dielectric strength, Liquid to Solid, Will keep
the pigments in suspension, impermeability.
21. Describe how a basic inhibitor works.
Ans. A basic inhibitor reacts with the substrate to create rust inhibitive salts (phosphate &
chromates),to “passivate” the surfaceand make it less reactive to oxidation and corrosion.
22. Which of the common extenders could not be used in whites and pastels?
Ans. Slate Flour.
23. How would the film be affected if pigment was added above the CPVC?
Ans. Permeable/ Porous, Low cohesive strength, Low gloss, low adhesion.
24. Which of the rust inhibitive pigments is the most common?
Ans. Zinc Phosphate.
25. Why are extenders used in paint formulation?
Ans. Add thickness and bulk at low cost, increase intercoat adhesion.
26. If chromium was used as a pigment, what colour would the paint be?
Ans. Green, Orange, Yellow.

16. 27. Why are plasticisers added to paint?
Ans. Increase flexibility, reduce brittleness. Modifies the film properties.
28. Two metals are commonly used as galvanic pigmentation, name them.
Ans. Zinc & Aluminium.
29. Why are driers added to oil based paint?
Ans. To ensure even through thickness drying. (Prevent wrinkling & rivelling)
30. What is meant by the term thixotropic?
Ans. Thickener, Anti- Settling Agent, aid to storage.
31. What is meant by the term aggregate when referring to paint?
Ans. Loosely adhering cluster of pigments and particles.
32. If an antioxidant was added to paint, what would it do?
Ans. Anti- Skinning agent. Prevents paint from forming a skin in the tin.
33. Give the names of two plasticisers.
Ans. Castor Oil, Coconut Oil.
34. What is meant by the term solution?
Ans. The resultant liquid after dissolving a solute in a solvent.
35. Give two examples of a solution.
Ans. Salt & water, sugar in water.
36. What is meant by the term dispersion?
Ans. A solid or liquid mixed in another liquid, where there is no solubility.
37. There are two types of dispersion, what are they?
Ans. Suspension & Emulsion.
38. If paint cures by chemical reaction is it reversible or convertible?
Ans. Convertible.
39. What type of polymerisation occurs in chemically curing paint?
Ans. Crosslinked.
40. Name a paint, which dries solely by solvent evaporation.
Ans. Any linear polymer paints. (Chlorinated Rubber, Vinyls, Emulsions)

17. 41. What is meant by non convertible?
Ans. Reversible. Can be returned to its original state if solvent is re- introduced or re- applied.
42. What is meant by non reversible?
Ans. Convertible. It is permanently altered to a new state after undergoing a chemical change.
43. Name four drying mechanisms.
Ans. Solvent Evaporation, Chemical Curing, Oxidation, Coalescence.
44. In a coating, which dries by solvent evaporation, what type of polymerisation occurs?
Ans. Linear.
45. What is another term for Fineness of Grind?
Ans. Degree of Dispersion.
46. Which generic types of paint dry by solvent evaporation followed by oxidation?
Ans. Natural Oils and Resins.
47. What type of polymer forms during oxidation?
Ans. Branched.
48. What term applies to paint drying at ambient temperatures?
Ans. Air Drying.
49. What is meant by the term coalescence?
Ans. To physically join together.
50. What is meant by the term pot life?
Ans. The after opening and mixing, in which the contents of the container must be used.
51. Name three curing agents used in epoxies?
Ans. Amides, Amines, Isocynates.
52. Is paint a solution or dispersion, qualify?
Ans. Dispersion, as the pigments must remain solid within the binder.
53. What is an exothermic reaction?
Ans. A chemical reaction, which is giving off heat.
54. What is meant by the term induction period?
Ans. The time after mixing, in which the paint should stand prior to use, to allow polymerization
(crosslinking) to begin and thorough wetting of the pigment particles to take place.

18. 55. What is the difference between ‘thermoplastic’ and ‘thermosetting’?
Ans. Thermosetting coatings will cure if heat is applied, and Thermoplastic coatings will deform if
heat is applied.
56. With a chemically curing paint, what type of polymerisation occurs?
Ans. Crosslinking.
57. Two other terms relate to induction period, what are they?
Ans. Stand Time & Lead Time.
58. Does a phenolic resin have an induction period?
Ans. No, (phenolic resin paints are not chemically curing).
59. Which of the following binders are reversible?
a) Epoxy
b) Phenolic
c) Vinyl
d) Urethane
e) Chlorinated rubber
f) Alkyd
g) Cellulose
h) Silicone
Ans. Chlorinated rubber, Vinyl, Cellulose.
60. Is an epoxy powder paint thermoplastic or thermosetting?
Ans. Thermosetting.
61. If a coating is permeable, what does it mean?
Ans. It will allow the passage of moisture or electrolyte.
62. What is meant by cross-linking, give two binders as an example.
Ans. Multi- directional polymerization, e.g. Epoxy, Urethane.
63. What is the opposite to exothermic?
Ans. Endothermic.
64. What is the term used for paints needing temperatures in excess of 65°C to cure?
Ans. Stove Drying.
65. What would be a typical induction period for chlorinated rubber paint?
Ans. None (it is not chemically curing).

19. 66. Name a material used as a dryer in paint formulation.
Ans. Heavy metal salts (such as Octoates and Napthanates of Cobalt, Manganese and Zirconium)
67. Why would bentonite or wax be used in paint formulation?
Ans. Thickeners, Thixotropic agents, Anti settling agents, Non- drip.
68. Name two materials used as plasticisers.
Ans. Coconut Oil, Palm Oil, Castor Oil.
69. What generic type of paints would use anti-oxidants?
Ans. Natural Oils & Resins.
70. How does a single pack, epoxy ester paint dry?
Ans. Solvent Evaporation followed by Oxidation.
71. How is dew point defined?
Ans. The temperature at which moisture, in the form of water vapour in air will condense.
72. How is relative humidity defined?
Ans. The amount of water vapour present in the air, expressed in percentage of the water vapour,
which “could be” in the air at that same temperature.
73. When using a whirling hygrometer which bulb should be read first and why?
Ans. The wet bulb should be read first, as it is artificially reduced and the temperature will gradually
rise back to ambient.
74. At what speed should the thermometer bulbs pass through the air?
Ans. Four metres per second (4 m/s), or as fast as possible.
75. What should be used when wetting the wick on whirling hygrometer?
Ans. De- Ionised or distilled water.
76. By what other name can we refer to a whirling hygrometer?
Ans. Aspirated psychrometer.
77. When the air temperature rises does the air’s capacity to hold water increase or decrease?
Ans. Increases.
78. What is the stated criterion for acceptance, prior to calculations, on a whirling hygrometer?
Ans. 2 consecutive identical readings (within 0.2 degrees).

20. 79. Name two pieces of equipment used for taking steel temperature.
Ans. Limpet Gauge (magnetic thermometer), touch pyrometer.
80. Is it possible for a wet bulb temperature to be higher than the dry bulb?
Ans. No, never.

21. Paint testing
1. Define viscosity.
Ans. A fluid’s resistance to flow.
2. What is meant by high viscosity?
Ans. Very thick and resisting flow.
3. Approximately, what is the viscosity of water?
Ans. 1 centipose or 1 dyne sec/cm².
4. Name the cgs and SI units of dynamic viscosity.
Ans. cgs = poise, SI = Nsec/m².
5. Name three different flow cups.
Ans. Ford, Zahn, Frikmar, ISO, ASTM.
6. When using a flow cup which unit of viscosity would be used?
Ans. Seconds.
7. In Ford Flow Cup No 4 what does 4 relate to?
Ans. Diameter of the flow hole.
8. Give the names of three different rotational viscometers.
Ans. Kerbs Stormer, Ford Flow Cup, Zahn, Rotothinner.
9. Give a reason for performing a viscosity test on site.
Ans. Test to determine the addition of thinners, and mix ratio of multi packs.
10. Which viscometer would not be used on thixotropic paint?
Ans. Flow Cup.
11. Why is temperature very important when doing viscosity tests?
Ans. Viscosity will reduce at raised temperatures.
12. What is the main difference between the rotathinner and Krebs Stomer?
Ans. Rotothinner is for dynamic viscosity and kerbs stormmer is for kinematic viscosity.
13. Describe how to use a Ford Flow Cup.
Ans. 100 cc paint, @ 20° C, scrape excess, allow to flow, measure in seconds until first break in
continuous flow.

22. 14. Give another name for a Fineness of grind gauge.
Ans. Hegman Grind Gauge.
15. Is a low flash point safer than a high flash point?
Ans. No.
16. How and for what is a Hegman grind gauge used?
Ans. To measure degree of dispersion or grind of fineness.
17. Briefly describe how to do the volatile, non-volatile test to BS 3900 Pt B2.
Ans. Weigh glass rod & plate, add 2g of paint, weigh again, stir and place in oven to evaporate
solvent. Remove and weigh again.
18. Name the equipment used to determine the flash point of a solvent.
Ans. Abel Cup.
19. What colour should the flame be at the flash point?
Ans. Blue.
20. What formula is used to calculate the density?
Ans. D= M/V.
21. What formula is used to calculate specific gravity?
Ans. Density of product/ Density of distilled water.
22. What is relative density?
Ans. Density compared to the distilled water.
23. What are the other names for a density cup?
Ans. Pyknometer, weight per litre cup, SG cup, weight per gallon.
24. What is a stoke, the unit for?
Ans. Kinematic viscosity.
25. Which test is used to determine abrasion resistance?
Ans. Erichson, Taber, Gardener.
26. Which equipment would be used to determine flexibility?
Ans. Conical Mandrel.
27. Which equipment would be used to measure impact resistance?
Ans. Tubular Impact tester.

23. 28. For what reason would the Koenig Albert apparatus be used?
Ans. Hardness of the film.
29. For which two reasons could a density cup be used on site?
Ans. Check addition of thinners, correct mixing ratio.
30. Name four accelerated test boxes.
Ans. Humidity cabinet, Salt spray cabinet, Temperature cycling, Prohesion test, Water soak test.
31. Why would a tropical box be used?
Ans. To test paints ability to withstand accelerated tropical conditions.
32. Would a paint be higher or lower density than water?
Ans. Higher.
33. How would the density be affected if solvent was added to paint?
Ans. Weight, (density) would be reduced.
34. What is the capacity of a density cup?
Ans. 100 cc.
35. What difference is there between SG and density?
Ans. Density has unit (g/cc), SG is the measure of the density of the product/100.
36. What information could be obtained from a water soak test?
Ans. Water absorption.
37. What information could be obtained from a temperature cycling test?
Ans. Contraction and expansion cracking.
38. What information could be obtained from a cold check test?
Ans. Contraction cracking.
39. Name four drying and curing tests.
Ans. Ballotini, BK stylus, Mechanical thumb test, Wolf- willborne pencil scratch.
40. What stage of the BK test would be recorded as the drying time?
Ans. When no scratch is evident whateverso.
41. Name three methods of determining opacity.
Ans. PFund Cryptometer, Hiding power charts plus adjustable applicator, Black/ White fused plate.

24. 42. What effects the opacity of a paint film?
Ans. Hiding ability is affected by CPVC.
43. Why would a Pfund cryptometer be used?
Ans. To determine the minimum DFT required to provide covering of the underlying substrate.
44. Give one reason why an inspector would use a PIG gauge?
Ans. To determine the minimum DFT required to provide covering of the underlying substrate.
Check DFT and correct coating sequence. Check DFT over ferrous materials (MIO). Or to check
DFT on Non Ferrous substrates.
45. Why are wet paint film thicknesses needed?
Ans. To calculate the DFT if volume solids is known, to ensure correct calculation of DFT.
46. Name two methods of measuring WFTs
Ans. Eccentric wheel, comb gauge, biscuit gauge.
47. What is the reason for taking WFTs immediately after application?
Ans. Prior to immediate solvent evaporation, to ensure correct calculation of DFT.
48. Where could an inspector find information to determine if a two-pack paint was mixed in the
correct proportions, using a density cup?
Ans. Manufacturers data sheet.
49. Can a banana gauge be used on non-ferromagnetic substrate?
Ans. No.
50. Could an eddy-current gauge be used on ferromagnetic substrates?
Ans. No. (Electromagnetic induction is used for ferrous).
51. Can a horseshoe gauge be used on non-ferromagnetic substrates?
Ans. No.
52. As part of which test would a bar applicator be used?
Ans. Hiding power charts and bar applicator (opacity).
53. Which instruments would be used to measure reflectivity?
Ans. Glossmeter.
54. How does a gloss meter work?
Ans. Measures the amount of received light from a known light source, at a given angle.

25. 55. Which factors in paint govern the degree of gloss?
Ans. CPVC, Binder type, Solvent type, refractive index, Degree of dispersion.
56. In a primer/mid coat what would be the expected degree of grind?
Ans. 40 microns.
57. In a gloss paint what would be a typical degree of grind?
Ans. Occasionally 10microns, but mainly 20 microns.
58. What percent reading would be expected when measuring gloss on a glass panel?
Ans. 100%.
59. Using a gloss meter a reading of 25% would signify what?
Ans. Matt.
60. If an aggregate size of 35µm was present in a paint of 30µm DFT what would be a likely result
when using a gloss meter?
Ans. Matt finish.
61. Name three common tests for determining adhesion of a paint film?
Ans. Cross cut, Dolly, HATE, V cut tests.
62. Which adhesion tests are quantitative?
Ans. Dolly, HATE.
63. Intercoat adhesion and primer to substrate adhesion are two adhesion faults name the third?
Ans. Cohesive failure.
64. What chemical solution is used to conduct a cathodic disbondment test?
Ans. 3% saltwater.
65. Which gas evolved at the cathode causes disbondment?
Ans. Hydrogen.
66. What criterion is used when assessing a cathodic disbondment test panel?
Ans. No more than 5mm damage outside of 6mm diameter hol, after 28 days.
67. Name the two methods of applying cathodic protection.
Ans. Sacrificial anode, impressed current.
68. What is used to determine the potential of a pipeline?

26. Ans. Copper/ copper sulphate, half cell reference electrode.
69. Would it be advisable to refill a pipe trench with carbonaceous backfill?
Ans. No, as the CP system would be nullified.
70. Does a cathodic protection system eliminate corrosion?
Ans. It controls the location and the rate of corrosion.
71. Can the external surface of a tank be protected?
Ans. No.
72. Could a crude oil tank be fully protected internally?
Ans. No. Only to the level of the tank contents.
73. What voltage would be used on a 250µm thick paint using a sponge type pinhole detector?
Ans. 9 volts.
74. What voltage would be used on a 450μm thick coating with a sponge type pinhole detector?
Ans. 67.5 volts.
75. When using a wet sponge, what other liquid is added to the water?
Ans. Detergent.
76. What function does the above additive perform?
Ans. Reduce surface tension, water softener.
77. Would it be advisable to do wet sponge detection on galvanising?
Ans. No because Zinc is conductive.
78. Why work upwards on a vertical surface with a wet sponge?
Ans. To avoid incorrect or erroneous flaw locations owing to water seepage.
79. Does a sponge detector work on AC or DC current?
Ans. DC.
80. Other than the wet sponge, which other equipment could be used to determine the presence of
pinholes/holidays?
Ans. High voltage holiday detector using wire brushes. (NOT SPRINGS)

27. Revision questions general
1. Name two categories of paint mill.
Ans. DIRECT Charge Mill, Premix Mill, Let down mill.
2. What is the main reason for processing paint in a mill?
Ans. Correct mix proportionate with requirements, fineness of grind.
3. Briefly describe how a ball mill works.
Ans. Steel balls tumbled in a horizontal rotating drum, grinding the mill base.
4. Briefly describe how an attritor mill works.
Ans. Vertical drum with motorized paddles driving the steel balls.
5. When would steel balls not be used in a ball mill?
Ans. When using a lighter coloured paints.
6. A bead mill is sometimes called by which other names?
Ans. Sand Mill, Pearl Mill.
7. How does a colloid mill work?
Ans. High speed stone discs bottom one rotating at 3600 rpm, top disc stationary.
8. Name eight items of information listed on a materials data sheet.
Ans. Pot life, shelf life, SG, flash point, drying time, application temperature, VS%, induction period,
mix ratio, application method and rate, orifice/ nozzle size, safety, Brand name and description,
batch number, solvent type, colour, coverage, storage conditions, binder type, recommended
surface preparation, overcoating time.
9. What do you understand from the term halogenated hydrocarbon?
Ans. Iodine, Flourine, Chlorine.
10. How can we determine the viscosity of a high viscosity paint?
Ans. Krebs- Stormer Viscometer.
11. Briefly describe the principles of CP.
Ans. It controls the location and rate of corrosion by means of an impressed current.
12. What function does a primer have in a paint system?
Ans. Protects the substrate by means of anti- corrosive or sacrificial pigments.
13. In a mordant primer what is the main working constituent?

28. Ans. Phosphoric acid.
14. What advantages do electrostatic application methods provide?
Ans. Good edge cover, good transfer, low waste, uniform thickness.
15. Which is the most expensive type of brush filling?
Ans. Natural hair.
16. What is cohesive failure in paint, give the main cause?
Ans. Solvent entrapment, incorrect mixing ratio, too high CPVC.
17. Why does a zinc rich paint need a strong binder?
Ans. Good cohesive strength is required with zinc, to provide sacrificial protection.
18. Why are etch primers not spray applied?
Ans. Toxic acid and environmentally unsafe
19. What do you understand by the term over spray?
Ans. Accidental spray on undesirable. (nameplates, instrumentation etc.)
20. Name four methods of determining DFTs.
Ans. WFT plus Calculations, PIG, electronic gauges, banana gauge, horseshoe gauge, tinsley pencil.
21. What is a psychrometer used for?
Ans. To measure wet bulb and dry bulb temperature.
22. What colour should a galvanised surface be after application of T wash?
Ans. Black.
23. How soon can a T washed substrate be coated?
Ans. As soon as it is dry.
24. Other than pigment, base and curing agent name two other constituents of FBE powder paint.
Ans. Anti foaming agent, wetting agent.
25. Give the main differences between airless and conventional spray.
Ans. Conventional gives better atomization, more accuracy, better finish, easier cleaning, specialized
container required, Airless gives higher deposition rate, less waste, faster, larger area coverage.
26. Brush application has advantages over spray application, what are they?
Ans. Small area, environmental friendly, cheaper, works paint into substrate, accessibility, thicker
application, very low waste, prevents pinhole, accuracy, no overspray.

29. 27. What is the main consideration when selecting a metallic pigment for a sacrificial paint?
Ans. Its position in the galvanic list.
28. What is meant by shererdizing?
Ans. Items are tumbled in zinc dust at a temp just below melting point.
29. Name three types of paint feed for a conventional spray.
Ans. Suction, gravity, remote pressure.
30. What is the calorising process?
Ans. Coating with aluminium.
31. Why would a sealer be applied to aluminium metal spray?
Ans. For high temperature service, to prolong protection.
32. What is the BS 2015 term for skipped or missed areas?
Ans. Holidays.
33. A colour has three properties, what are they?
Ans. Hue, Brightness and saturation.
34. Why would paint be applied by hot spray?
Ans. To reduce viscosity.
35. On an airless spray tip how are blockages cleared?
Ans. Twist the nozzle.
36. How is atomisation achieved using conventional sprays?
Ans. Airstream convergence outside of the nozzle.
37. How is atomisation achieved using airless sprays?
Ans. Explosive force of high pressure paint meeting low pressure air.
38. What is dip coating?
Ans. Dipping the item in a tank of paint, allowing to dry.
39. What do you understand from the term ropiness?
Ans. Brushmarks.
40. What is efflorescence and how does it occur?
Ans. Soluble salts, normally deposited on concrete and mortar work.

30. 41. Name two ways of melting aluminium to enable it to be sprayed.
Ans. Electric arc, wire and pistol.
42. What is flocculation?
Ans. Loosely clustered particles or aggregates often found in out-of-date paint.
43. What could be the cause of bittiness in a paint film?
Ans. Foreign Bodies in the paint. (grit, dust etc.)
44. What is a tie coat?
Ans. A coat of paint applied to an area adjoining two incompatible coating systems.
45. How many depressions of the bellows are needed for the Dräger test?
Ans. Varies according to the relevant crystals required for the solvent under test.
46. What are the hazard signs for Toxic, Very Toxic, Harmful and corrosive?
Ans.
47. What is saponification?
Ans. The production of lead soaps, when using basic primer with Natural Oil paints.
48. What units are used for measuring toxicity?
Ans. PPM (parts per million).

31. 49. Which material would have to be used on a perpetually damp surface?
Ans. Moisture curing Polyurethane.
50. What is padding?
Ans. Use a pad, coated in fine natural hair, to apply paint.
51. What air inlet pressure is needed to give 2500 psi delivery with 35:1 pump?
Ans. 71 psi.
52. What causes lifting of a paint film?
Ans. Non-observance of overcoating time, applying strong solvent over weakbinder.
53. What is cissing and how is it caused?
Ans. Oil or grease contamination of the substrate, causing a local lack of adhesion.
54. What is meant by the abbreviations: OES, OEL, MEL, UEL, LEL and RAQ?
Ans. Occupational Exposure Standard, Occupational Exposure Limit, Maximum Exposure Limit,
Maximum Exposure Limit, Lower Exposure Limit, Required Air Quantity.
55. Why would a paint inspector use potassium hexacyonoferrate?
Ans. Check for hygroscopic salt contamination.
56. What would be an average thickness for galvanising?
Ans. 100 µm.
57. How can you tell the difference between blooming and chalking?
Ans. No.
58. What could be the reasons for inter coat adhesive failure?
Ans. Incompatibility, contamination.
59. How would you determine quality of added thinners in thixotropic paint?
Ans. Rotational Viscometer.
60. Why are manufacturers developing solvent free, water borne and powders?
Ans. Environmental Impact, Cost.
61. What would be the cause of grinning on a paint film?
Ans. Poor opacity, Low CPVC.
62. How can bleeding be avoided?
Ans. Total removal of bitumen/ Coal Tar coatings prior to painting.

32. 63. In less than 30 words, explain the duties of a painting inspector.
Ans
i. Visually inspect paint finish.
ii. Measure & report wet bulb & dry bulb, DP, RH.
iii. Control storage of paint and abrasives.
iv. Monitor against re- use of abrasives.
v. Monitor compliant materials.
vi. Check surface condition & preparation.
vii. Record Weather conditions & compliance with specification.
viii. Measure and record surface profiles.
ix. Prepare inspection reports.
x. Check adherence to Pot- Life & Induction period.
xi. Measure & record DFT, WFT.
xii. Report any Non- Conformance to Engineer.
xiii. Check operation of blasting equipment (vapour traps earth cable, whiplash cables, external
couplings etc.).
xiv. Should have Site Plan and documentation.
xv. Monitor intercoat time.
xvi. Painting sequence.
xvii. Monitor addition of thinners.
xviii. Preparation of Q panels or test plates.
xix. Administering adhesion tests.
64. Name five documents, which a painting inspector might need on a contract.
Ans. Contract specification, Inspection Reports, Operator Qualifications, COSHH.
65. What information should be given on a daily report sheet?
Ans. WFT, DFT, DP, RH, Wet bulb & Dry bulb Temperature, time, operator name, paint system, steel
temp, paint batch number, air temp, weather conditions, wind speed, measured surface profile,
paint batch number, paint manufacturer, colour code, application date, expiry or shelf life date,
induction period (if applicable) Client, Contract, report number, abrasive type, rust grade,
location, abrasive size, abrasive supplier, overcoating time, method of cleaning, inspector name
and qualification, blast grades, standard.
66. Curtains, Sags, Runs and Tears are a result of what?
Ans. Excessive paint deposition.
67. Some binders can be modified to use water as a solvent, name four.
Ans. Vinyls, acrylics, emulsions, Alkyds, Bitumens.
68. What is meant by the term stripe coat?

33. Ans. Brush applying a coat of paint where spray application may be inaccessible.
69. How many cm3 are there in 4.5 litres?
Ans. 4500.
70. A paint data sheet provides a wealth of information, name eight items.
Ans. Flash Point, Density, VS%, Health & Safety, Batch Numbers, recommended thinners, Drying
time at 20°C, recommended WFT, Application method, contents, Solvent Type.

34. Revision questions PA 10 specific
1. What is the specified course of action for grit inclusions?
Ans. Reblast and re- coat.
2. The term long term protection refers to what?
Ans. Protection lasting typically 10 years.
3. What is the difference between new and weathered galvanising?
Ans. Weathered surface provides its own key, and requires only stiff bristled brush for preparation.
4. What criterion determines which paint system should be used?
Ans. The compatibility with the existing coating system, and must be, in accordance with PA 10.
5. What is the total DFT of the compliant epoxy system?
Ans. 265 microns.
6. What is the total DFT of the water borne system?
Ans. 225 microns.
7. When can ladders and other means of access be removed?
Ans. When all operations (including final acceptance) have been completed.
8. Two materials are specified for used on damp surfaces, what are they?
Ans. Moisture Curing Plyurethane, Solvent Free Epoxy.
9. After removal of a non-drying paint, which type of primer is recommended?
Ans. A WHITE SPIRIT BASED PRIMER.
10. Some non-ferrous substrates are painted for aesthetics only, name four.
Ans. Stainless Steel, Concrete, Fibre Glass, Aluminium.
11. Which three non-ferrous substrates are painted for anti corrosion purposes?
Ans. New galvanized, weathered galvanized, previously painted galvanizing.
12. According to PA 10 in which situations would T wash be used?
Ans. New galvanized, where sweep blasting or hand abrasion is inadvisable or impractical.
13. How many coats of primer are specified on surfaces at 100-149°C?
Ans. As many as required.
14. Give preferential order of coating systems for surfaces 150-340°C.
Ans. TSA, IZC, PIC.

35. 15. Is it mandatory for a contractor to produce a test area?
Ans. Not mandatory, but generally upon request.
16. List four items needing masking off prior to blasting and painting.
Ans. Name plates, instrumentation, vents, monitoring panels.
17. Which Aluminium substrate would not be sweep blasted?
Ans. Thin Aluminium plate.
18. Which three paint systems are specified for use on aluminium?
Ans. Water Borne Acrylic, High Build Epoxy, Alkyd or modified alkyd.
19. What differences are there in new and maintenance painting specifications for substrates below
100°C?
Ans. Exisiting coating type (compatibility), surface preparation (new= blasting/ maintenance
painting= hand and power tools. Environmental conditions. Access to area, application
methods, overlap with maintenance painting 100mm onto sound coating (feathering onto
sound coating).
20. Toxic coatings need special considerations for removal from substrates, name two methods
which comply.
Ans. Needle Gun, Water Jetting, Water Plus Abrsive.
21. In which situations is a Permit to Work required?
Ans. All BGAS installations (live sites).
22. Which primers are specified for non-weathered galvanising?
Ans. Wash Primers, such as T- Wash.
23. Which primers are specified for weathered galvanising?
Ans. Primer not required, initial coat MIO.
24. According to PA10 is flame cleaning allowed?
Ans. No, not on live Gas sites.
25. According to PA10 is thinning of paint allowed?
Ans. Yes, but only in accordance with the manufacturers data sheets.
26. What temperature range is covered by ‘hot duty service’?
Ans. Above 100° C.

36. 27. Does PA10 cover internal coatings on pipes?
Ans. No, not at live Gas sites.
28. What is the specified overlap on repair areas?
Ans. 100 mm onto sound coating.
29. What would be the specified surface preparation and coating system for aluminium cladding?
Ans. Blast cleaning to Sa3 (check for mill scale) profile 75 µm MAX.
30. What would be the procedure for removal of algae and mould?
Ans. Treat with a biocidal agent for 24 hours, then scrub with stiff bristle brush and water power
washing.
31. What would be the procedure for degreasing prior to surface preparation?
Ans. Degrease using a non aliphatic solvent (xylene) and then scrub with detergent.
32. What would be the procedure for degreasing after to surface preparation?
Ans. Using a smaller size abrasive or using hand and power tools.
33. When blast cleaning on an AGI what precautions are taken?
Ans. All blast cleaning done in accordance to IGE SR 21 and ensure that a permit to work is in place
and also a hot work permit.
34. Is it permissible to prepare paint by stirring?
Ans. Only if the volume of the paint is less than 5L otherwise use a mechanical agitator.
35. What would be the surface preparation method for new galvanising?
Ans. Sweep Blast (Sa1).
36. When would it be necessary to apply a sealer to inorganic zinc silicate?
Ans. When long term protection is required.
37. How could areas of a paint breakdown be prepared for repainting?
Ans. Sweep blasting, emery paper.
38. What information should be on a paint can label for BG?
Ans. Hazard warning symbol, batch number, paint type, colou.
39. When measuring DFTs over galvanising what allowances are made?
Ans. Deduct the thickness of the zinc, generally 100 micron.
40. What is the first coat applied to galvanised substrates and why?

37. Ans. MIO, primer is not required because the zinc acts as a sacrificial primer much like the
aluminium primer.
41. Properties and Performances of paint are covered in which BG specification?
Ans. BGC/ PS/ PA9.
42. What are the considerations when selecting a paint system?
Ans. Existing coating if any (compatibility), surface temperature, environment, lifetime expectancy,
cost, cleaning methods.
43. According to PA 10 which two coats are applied at works?
Ans. Primer and MIO.
44. Give the criterion for when and when not, painting can take place.
Ans. Max. 90% Relative Humidity, Steel & Air Temperature to be 3° C above Dew Point.
45. What should be the substrate reaction when T wash is applied to a newly galvanised substrate?
Ans. The substrate turns black.
46. Which two materials are specified for use on damp surfaces?
Ans.Moisture Curing Polyurethane, Solvent- free epoxies.
47. What is the maximum time lapse from surface preparation to coating?
Ans. 4 hours.
48. Which is the most common pigment used in high temperature paints?
Ans. Silicones.
49. What would be the result of over thick application of zinc silicate?
Ans. Mud cracking.
50. According to PA10 is roller application permissible?
Ans. PA10 states that Roller application is not recommended.

38. B Gas 3.2 Maths Exercises
WFT calculations
1. What WFT would need to be applied to give a DFT of 45μm using a paint of 56% vs?
Ans. Given:-
DFT= 45 µm. VS= 56%. WFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
So,
𝑊𝐹𝑇 = (
100
56
) 𝑋 45
𝑊𝐹𝑇 = 80.35 µ𝑚.
2. What WFT would need to be applied to give a DFT of 60μm using a paint of 40% vs?
Ans. Given:-
DFT= 60µm. VS= 40%. WFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
So,
𝑊𝐹𝑇 = (
100
40
) 𝑋 60
𝑊𝐹𝑇 = 150 µ𝑚.
3. A paint of 38% vs was used to give a DFT of 45μm what would be the WFT?
Ans. Given:-
DFT= 45µm. VS=38%. WFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
So,
𝑊𝐹𝑇 = (
100
38
) 𝑋 45
𝑊𝐹𝑇 = 118.42 µ𝑚.
4. A DFT of 55μm was obtained from a paint of 55% vs, what was the WFT applied?
Ans. Given:-
DFT= 55µm. VS= 55%. WFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇

39. So,
𝑊𝐹𝑇 = (
100
55
) 𝑋 55
𝑊𝐹𝑇 = 100 µ𝑚.
5. What WFT would be applied to leave a DFT of 65μm using a paint of 49% vs?
Ans. Given:-
DFT= 65µm. VS= 49%. WFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
So,
𝑊𝐹𝑇 = (
100
49
) 𝑋 65
𝑊𝐹𝑇 = 132.65 µ𝑚.
DFT calculations
1. What would be the DFT if 20 litres of paint, vs. 45% covered an area of 9m x 12m?
Ans. Given:-
Volume= 20 litres. VS= 45%. Area= 9m × 12m = 108m².
We know that,
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
𝑊𝐹𝑇 = 𝑉 × (
1000
𝐴
)
And,
𝐷𝐹𝑇 = 𝑊𝐹𝑇 × (
𝑉𝑆
100
)
Therefore,
𝑊𝐹𝑇 = 20 × (
1000
108
)
𝑊𝐹𝑇 = 185.2 µ𝑚.
So,
𝐷𝐹𝑇 = 185.2 × (
45
100
)
𝐷𝐹𝑇 = 83.34 µ𝑚.
2. 25 litres of paint, vs. 65% was used to cover a circular area of 10m diameter. What would be the
resulting DFT?
Ans. Given:-
Volume= 25 L. VS= 65%. Diameter= 10m. Area= πr² = 3.14 × (5)² =78.5m².
We know that,

40. 𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
𝑊𝐹𝑇 = 𝑉 × (
1000
𝐴
)
And,
𝐷𝐹𝑇 = 𝑊𝐹𝑇 × (
𝑉𝑆
100
)
Therefore,
𝑊𝐹𝑇 = 25 × (
1000
78.5
)
𝑊𝐹𝑇 = 318.48 µ𝑚.
So,
𝐷𝐹𝑇 = 318.48 × (
65
100
)
𝐷𝐹𝑇 = 207 µ𝑚.
3. What DFT would be obtained if a paint vs content 42% was applied at a WFT of 84μm?
Ans. Given,
WFT= 84µm. VS= 42%. DFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝐷𝐹𝑇 = 𝑊𝐹𝑇 × (
𝑉𝑆
100
)
So,
𝐷𝐹𝑇 = 84 × (
42
100
)
𝐷𝐹𝑇 = 35.28 µ𝑚.
4. With a WFT of 130μm, using a paint containing 83% VS, what would be the resulting DFT ?
Ans. Given,
WFT= 130µm. VS= 83%. DFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝐷𝐹𝑇 = 𝑊𝐹𝑇 × (
𝑉𝑆
100
)
So,
𝐷𝐹𝑇 = 130 × (
83
100
)
𝐷𝐹𝑇 = 107.9 µ𝑚.
5. A paint, VS 65% was applied at a WFT of 130μm, what would be the resulting DFT?

41. Ans. Given,
WFT= 130µm. VS= 65%. DFT=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝐷𝐹𝑇 = 𝑊𝐹𝑇 × (
𝑉𝑆
100
)
So,
𝐷𝐹𝑇 = 130 × (
65
100
)
𝐷𝐹𝑇 = 84.5 µ𝑚.
VS calculations
1. A DFT of 53µm was obtained from a WFT of 110µm, what was the vs% of the paint?
Ans. Given,
DFT= 53µm. WFT= 110µm. VS=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉𝑆 = (
100
𝑊𝐹𝑇
) 𝑋 𝐷𝐹𝑇
So,
𝑉𝑆 = (
100
110
) 𝑋 53
𝑉𝑆 = 48.18 %.
2. A paint was applied at 120µm WFT. The resulting DFT was 65µm, what was the vs%?
Ans. Given,
DFT= 65µm. WFT= 120µm. VS=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉𝑆 = (
100
𝑊𝐹𝑇
) 𝑋 𝐷𝐹𝑇
So,
𝑉𝑆 = (
100
120
) 𝑋 65
𝑉𝑆 = 54.17 %.
3. What would be the vs% of a paint if it was applied with a WFT of 120µm and a DFT of 68µm was
obtained?
Ans. Given,
DFT= 68µm. WFT= 120µm. VS=?

42. We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉𝑆 = (
100
𝑊𝐹𝑇
) 𝑋 𝐷𝐹𝑇
So,
𝑉𝑆 = (
100
120
) 𝑋 68
𝑉𝑆 = 56.67 %.
4. What was the vs% of a paint with a DFT of 36µm, when the WFT was 108µm?
Ans. Given,
DFT= 36µm. WFT= 108µm. VS=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉𝑆 = (
100
𝑊𝐹𝑇
) 𝑋 𝐷𝐹𝑇
So,
𝑉𝑆 = (
100
108
) 𝑋 36
𝑉𝑆 = 33.33 %.
5. A DFT of 62µm was measured, from a WFT application of 100µm, what would be the vs% of the
paint used?
Ans. Given,
DFT= 53µm. WFT= 110µm. VS=?
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉𝑆 = (
100
𝑊𝐹𝑇
) 𝑋 𝐷𝐹𝑇
So,
𝑉𝑆 = (
100
110
) 𝑋 53
𝑉𝑆 = 48.18 %.
Volume calculations
1. What volume of paint would be required to cover an area of 300 square metres, to a specified
DFT of 65µm, using a paint of 45% vs?
Ans. Given,
DFT= 65µm. VS= 45%. Area = 300m².

43. We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
Therefore,
𝑊𝐹𝑇 = (
100
45
) 𝑋 65
𝑊𝐹𝑇 = 144.44 µ𝑚.
So,
𝑉 = 300 × (
144.44
1000
)
𝑉 = 43.33 𝐿.
2. How much paint would be required to coat a tank, roof and side sheets to a DFT of 100µm? The
tank is 5 metres diameter and 6 metres high. The paint to be used is solvent free.
Ans. Given,
DFT= 100µm. WFT= 100µm. (same as DFT, Because Paint is solvent free)
VS= 45%. D= 5m. H= 6m.
Area = πr² + 2πrh = 3.14× (2.5)² + 2×3.14×2.5×6 = 94.2+19.625 = 113.83m².
We know that,
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
So,
𝑉 = 113.83 × (
100
1000
)
𝑉 = 11.38 𝐿.
3. How much paint would be needed to cover a circular area of 10 metres diameter, using a paint
65% vs to a DFT of 60µm?
Ans. Given,
DFT= 60µm. VS= 65%. D= 10m. Area = πr² = 3.14× (5)²= 78.5m².
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
Therefore,
𝑊𝐹𝑇 = (
100
65
) 𝑋 60
𝑊𝐹𝑇 = 92.3 µ𝑚.
So,

44. 𝑉 = 78.5 × (
92.3
1000
)
𝑉 = 7.24 𝐿.
4. A circular area of 7 metres radius is to be coated to a DFT of 45µm. What volume of paint would
be required if the vs content was 48%?
Ans. Given,
DFT= 45µm. VS= 48%. R= 7m. Area = πr² = 3.14× (7)²= 153.86m².
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
Therefore,
𝑊𝐹𝑇 = (
100
48
) 𝑋 45
𝑊𝐹𝑇 = 93.75 µ𝑚.
So,
𝑉 = 153.86 × (
93.75
1000
)
𝑉 = 14.42 𝐿.
5. How much paint would be needed, at 55% vs, to coat an area of 250 square metres to a DFT of
60µm?
Ans. Given,
DFT= 60µm. VS= 55%. Area = 250m².
We know that,
𝑊𝐹𝑇 = (
100
𝑉𝑆
) 𝑋 𝐷𝐹𝑇
𝑉 = 𝐴 × (
𝑊𝐹𝑇
1000
)
Therefore,
𝑊𝐹𝑇 = (
100
55
) 𝑋 60
𝑊𝐹𝑇 = 109.1 µ𝑚.
So,
𝑉 = 250 × (
109.1
1000
)
𝑉 = 27.27 𝐿.
Density and SG exercise
1. What would be the weight of 16.5 litres of paint with a SG of 1.45?
Ans. Given,

45. Volume= 16.5 L = (16.5×1000)cc = 16500cc. SG= 1.45.
Therefore,
Density(ρ) = 1.45 g/cc.
We know that,
𝜌 =
𝑚
𝑣
So,
1.45 =
𝑚
16500
𝑚 = 1.45 × 16500
𝑚 = 23925𝑔𝑚 𝑜𝑟 23.925𝑘𝑔.
2. What is the density of a paint if 7.5 litres weighs 9.75kg?
Ans. Given,
V= 7.5L= 7500cc. m= 9.75kg=9750gm.
So,
𝜌 =
𝑚
𝑣
𝜌 =
9750
7500
𝜌 = 1.3 𝑔/𝑐𝑐.
3. What would be the relative density of paint in question two?
Ans. Given,
ρ (density of paint)= 1.3g/cc. ρ₂ (density of water)= 1g/cc.
We know that,
𝑆𝐺 =
𝜌
𝜌₂
So,
𝑆𝐺 =
1.3
1
𝑆𝐺 = 1.3
4. If the weight of 25 litres of paint is 37.5kg, what would be the SG?
Ans. Given,
V= 25L = 25000cc . m= 37.5kg= 37500gm.
We know that,
𝜌 =
𝑚
𝑣
𝑆𝐺 =
𝜌
𝜌₂
Therefore,
𝜌 =
37500
25000
𝜌 = 1.5 𝑔/𝑐𝑐.

46. So,
𝑆𝐺 =
𝜌
𝜌2
𝑆𝐺 =
1.5
1
𝑆𝐺 = 1.5
5. A two-pack epoxy should be mixed at one part base to one part activator, the base has a density
of 1.4gm/cc and the activator 0.9gm/cc. What would be the density of the mixed components?
Ans. Given,
One part base at 1.4g/cc = 1.4g
Two parts activator at 0.9g/cc = 1.8g
Therefore total weight = 3.2g
Total volume for weight = 2cc
Density of mix =
3.2
2
= 1.6𝑔/𝑐𝑐.
6. A two-pack paint is mixed at a ratio of six parts pack A (density 1.3gm/cc) to one part pack B
(density 0.9gm/cc). What would be the density of the combined parts?
Ans. Given,
Six parts base at 1.3g/cc = 7.8g
One parts activator at 0.9g/cc = 0.9g
Therefore total weight = 8.7g
Total volume for weight = 7cc
Density of mix =
8.7
7
= 1.24𝑔/𝑐𝑐.
7. A mixed two-pack paint has a density of 1.35gm/cc. The density of the base was 1.5gm/cc and
the activator 0.9gm/cc. The mixing ratio was 3:1. Has the paint been mixed correctly?
Ans. Given,
Three parts base at 1.35g/cc = 4.05g
One parts activator at 0.9g/cc = 0.9g
Therefore total weight = 4.95g
Total volume for weight = 7cc
Density of mix =
4.95
7
= 0.70𝑔/𝑐𝑐.

47. 8. A mixed two-pack paint has a density of 1.35gm/cc. Mixed at a ratio of 6:1, base density
1.45gm/cc, activator density 0.95gm/cc. Has the paint been mixed correctly?
Ans. Given,
Six parts base at 1.35g/cc = 8.1g
One parts activator at 1.45g/cc = 1.45g
Therefore total weight = 9.55g
Total volume for weight = 7cc
Density of mix =
9.55
7
= 1.36𝑔/𝑐𝑐.