corrosion-mitigation techniques

2. WHAT IS CORROSION?
CORROSION IS A NATURAL PROCESS WHICH CONVERTS A MATERIAL INTO IT’S MORE
CHEMICAALY STABLE FORM.
IT IS THE GRADUAL DESTRUCTION OF MATERIALS BY CHEMICAL OR ELECTROCHEMICAL
REACTION WITH THEIR ENVIRONMENT
CORROSION OCCURS WHEN METAL IS EXPOSED TO MOISTURE OR OTHER CHEMICALS

4. MITIGATION TECHNIQUES:
MITIGATION TECHNIQUES ARE TECHNIQUES USED TO PREVENT CORROSION.
MITIGATION LITERALLY MEANS “REDUCTION OF SOMETHING”.
CORROSION CAN BE MITIGATED IN TWO WAYS:
◦ TECHNICAL APPROACH
◦ MECHANICAL APPROACH
WHY SHOULD WE PREVENT CORROSION?
◦ IT CREATES HUGE LOSS IN INDUSTRIAL SECTOR
◦ TO IMPROVE DURABILITY OF THE METALLIC SUBSTANCES

16. TYPES OF ENAMELS
Floor enamel – May be used for concrete, stairs, basements, porches, and patios.
Fast dry enamel – Can dry within 10–15 minutes of application. Ideal for refrigerators,
counters, and other industrial finishes.
High-temp enamel – May be used for engines, brakes, exhaust, and BBQs.
Enamel paint is also used on wood to make it resistant to the elements via the waterproofing
and rotproofing properties of enamel. Generally, treated surfaces last much longer and are much
more resistant to wear than untreated surfaces.
Epoxy enamel, Polyurethane Enamel etc used in protective coating / industrial painting purpose
in chemical and petrochemical industries for anti corrosion purposes.

17. ENAMEL CONTAINS SMALL PORES,WHICH
MAY CAUSE THE FORMATION OF PITTING
CORROSION.THE INTERFACE OF STEEL AND
ENAMEL REACTS AND CAUSES HYDROGEN
RECOMBINATION THAT LEADS TO THE
CREATION OF FISH SCALING AND SPALLING.

38. VAPOUR PHASE CORROSION
INHIBITORS:
Organic compounds with vapour pressure about 10^-7
to 10^-2mm Hg.
HOW DOES VCI PREVENT CORROSION?
Transport by diffusion through gas phase and adsorbed
onto the metal with a thickness of few
monolayers,thereby protecting it from corrosion.
VCI's are especially useful for protecting metals
incavities and other hard to reach places.

39. FACTORS
The efficiency of the inhibitor depends on
>adsorption ability
>strength of adsorption
>temperature
All these properties depend upon the chemical structure of the inhibitor.

40. VAPOUR PRESSURE OF INHIBITOR
A critical parameter in determining the VCI's effectiveness.
The transport mechanism requires VCI to possess an optimum vapour pressure.
If the vapour pressure is very low,it leads to slow establishment of a
protective layer.
If the vapour pressure is too high,VCI's effectiveness will be limited to a shorter
timeperiod.
For practical purposes,it is preferable to use less volatile inhibitors that provide
long-lasting and durable protection over periods of 2 years to 3 years.

41. SOME CLASSES OF VCI's
AMINES
ALIPHATIC AMINES
 volatile corrosion inhibitors .
 Aliphatic and alicyclic amines exhibit inhibitor
efficiencies superior to aromatic substances.
Most effective are the primary straight chain
amines with an even number of carbon atoms.
EXAMPLE:
cyclohexylamine,dicyclo
hexylamines,dicyclohexyl
ammoniumnitrite(DICHAN)

42. HETEROCYCLIC AMINES
EXAMPLES:
piperdine,hexamethylene imine,morpholine.
AMINO KETONES
 Have 2 heteroatoms with free electron pairs-one pair on thenitrogen and two
pairs on the oxygen of the ketonic group.
alpha amino ketones are more effective inhibitors than beta and gamma
amino ketones.

43. HYDROPHOBIC AND SUPERHYDROPHOBIC
Property of a substance to
repel water or fail to mix with
water
Examples : plants leaf ,birds
feathers ,waxes ,fats and oils.

44. A nanoscopic coating whose main function is to protect the
surface from water and to repel water.
Properties:
self-cleaning properties
dirt retention
corrosion resistant.
extended life
moisture resistant.
SUPERHYDROPHOBIC COATINGS

45. HYDROPHOBICITY TO
SUPERHYDROPHOBICITY
WATER CONTACT ANGLE:
 if angle <90 – hydrophilic
 if angle >=90 and <=150 –hydrophobic
 if angle >150 - superhydrophobic

46. CONTACT ANGLE HYSTERISIS:
- difference between advancing contact angle and the receding contact
angle.
For superhdrophobicity,
CAH<10 degrees
HYDROPHOBICITY TO
SUPERHYDROPHOBICITY

47. LOTUS EFFECT
Self cleaning property.
Dirt particles are picked up by the
water droplets due to
ultrahydrophobicity.
These properties are also found in
other plants like cane and in the wings
of certain insects.

48. SUPERHYDROPHOBIC
COATING
MATERIALS USED
FACTORS DETERMINING SUPERHYDROPHOBICITY
 SURFACE MORPHOLOGY
 SURFACE ENERGY

49. CORROSION CONTROL
Corrosion-due to presence of water or moisture.
Control:
 decreasing the surface energy
 water contact angle reaches 170 degrees.

50. FABRICATION OF SUPERHYDROPHOBIC
MATERIALS
Surface roughness.
Surface modification ,reducing surface energy.
materials:
 polymeric- hydrophobic, which after fabrication will produce
superhybrophobicity
 inorganic- hydrophilic, so surface hydrophobic treatment must be
done followed by surface modification

51. APPLICATIONS
windshields and architecture coatings
Separation of oils and water
Anti-bacterial adhesion
Self -cleaning –self-cleaning glasses
- self-cleaning textiles