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Surface finishing processes - Electroplating

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The presentation takes into account widely used surface finishing processes including electroplating, anodizing, alodining, cadmium plating, zinc plating, phosphating, passivation

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Surface finishing processes - Electroplating

  1. 1. Surface Finishing Processes By Hassan Habib
  2. 2. Table of Contents 1. 2. 3. 4. 4.A 4.B 4.C 4.D 4.E 4.F What is surface finishing? What is Electroplating? Anodizing Zinc Plating Phosphating Why we use electroplating? Types of electroplating? Alodining Cadmium Plating Passivation
  3. 3. What is surface finishing? Surface Finishing is a set of processes that we use to achieve desired mechanical properties on different products 1Purpose
  4. 4. What is surface finishing? • Mechanical properties are desired in products as per the intended use e.g toothpaste, non-stick utensils, impeller blade • One of the most widely used process of achieving desired qualities is electroplating • Electroplating is the most widely used process, used in variations to achieve desired properties 1Purpose
  5. 5. Why we use electroplating? Electroplating is used to deposit a foreign material on mechanical parts to protect them from corrosion, wear and tear and to increase visual aesthetics in some cases 2Purpose
  6. 6. What is electroplating? 3Process Anode •Metal to be plated Cathode •Part to be plated Sulphate solution of the same metal Electroplated Part
  7. 7. Types of surface finishing processes Following types of surface finishing processes are being used world wide: • Anodizing (MIL-A-8625F, MIL-STD-171E, ASTM B-766-86) • Alodining (MIL-STD-5541C, MIL-DTL-16232G) • Zinc Plating (ASTM-B-117, B-633) • Cadmium Plating (DEF-DTD-904) • Phosphation (DOD-P-16232 F) • Passivation (QQ-P-35B) 4Types
  8. 8. 4.A Anodizing
  9. 9. Anodizing Formation of a chemical conversion coating on metal surface by anodic oxidation is called anodizing. This process is carried out on aluminum and aluminum alloys or titanium alloys 4 A Purpose
  10. 10. Anodizing 4 A Process Jigging Degreasi ng Cleaning Anodizin g Dyeing Sealing Anodized Part
  11. 11. According to MIL-STD-8625 E: Type I – Chromic acid anodizing, conventional coatings produced from chromic acid bath Type IB – Chromic acid anodizing, low voltage process, 22 ± 2V Type IC – Non-chromic acid anodizing, for use as a non-chromate alternative for Type I and IB coatings Type II – Sulfuric acid anodizing, conventional coatings produced from sulfuric acid bath Type IIB – Thin sulfuric acid anodizing, for use as a non-chromate alternative for Type I and IB coatings Type III – Hard Anodic Coatings Class 1 – Non-dyed Class 2 – Dyed 4 A AnodizingTypes and Classes
  12. 12. • Bath Concentration = 10% H2SO4 • Current Density = 10-15 A/ft2 • Time = Depending upon requirement • Temperature = 18oC-22oC 4 A AnodizingProcess Specifications
  13. 13. 4 A AnodizingProcess Tests Test Type Applicable Specimen Preparation Requirement Test method Coating Weight I, IB, IC, II, IIB, III Specimen Panels: (min width 3 in, min thickness 0.032 in) 3.7.1.1 3.7.2.1.1 - ASTM B 244 - Weigh - Metallographic Microscope Coating Thickness III Specimen Panels: (min length 3 in, min width 3 in, min thickness 0.032 in) 3.7.2.1 - Weigh after stripping of coating Corrosion Resistance I, IB, IC, II, IIB Specimen Panels: (min length 10 in, min width 3 in, min thickness 0.032 in) 3.7.1.2 - Salt Spray test for 336 hrs Light Fastness I, IB, IC, II, IIB for Class 2 only Specimen Panels: (min length 10 in, min width 3 in, min thickness 0.032 in) 3.7.1.3 - Ultraviolet Radiation exposure for 200 hrs Abrasion Resistance III Specimen Panels: (min length 4 in, min width 3 in, min thickness 0.063 in) 3.7.2.2 - CS 1000 g wheels at 70 rev/min for 10,000 cycles.
  14. 14. 4 A AnodizingAdvantages • Highly Durable • Inexpensive to produce and maintain • Won’t chip, flake, peel or chalk • Maintains metallic appearance of aluminum • Environmental Friendly - No heavy metals - By products aid municipal waste water treatment facilities to separate solids and neutralize pH • Fire Protection - Anodic oxide layers give a minor increase in the fire protection of aluminum constructions. The melting point of the oxide surface increases from approximately 650oC to approximately 2000oC
  15. 15. 4.B Alodining
  16. 16. Alodining Alodining is the chemical application of a protective chromate conversion coating on alumiunum 4 B Purpose
  17. 17. Alodining 4 B Process Alkaline Cleaning Rinsing Deoxidati on Rinsing Chromat e Coating Rinsing Alodined Part
  18. 18. According to MIL-STD-5541 C: Class 1A – For minimum protection against corrosion resistance. Good quality for the surfaces to be painted or not Class 3 – For protection against corrosion where lower electrical resistance is required. 4 B AlodiningClasses
  19. 19. 4 B AlodiningProcess Tests Test Class Applicable Specimen Preparation Test method Corrosion Resistance 1A, 3 Specimen Panels: (min length 10 in, min width 3 in, min thickness 0.02 in) - Salt Spray test for 168 hrs Adhesion wet tape 1A, 3 Specimen Panels: (min length 10 in, min width 3 in, min thickness 0.02 in) - Adhesion Wet Tape Test Electrical resistance testing 3 Specimen Panels: (min length 4 in, min width 3 in, min thickness 0.063 in) - At 200 psi nominal electrode pressure class 3 must not have resistance greater then 5000 microhms
  20. 20. 4 B AlodiningAdvantages • Adds no measurable weight • Does not alter the dimensions of parts (does not make holes smaller) • Requires essentially no cleanup after application. Encourages treatment of all small parts as they are fabricated and installed • Requires no electricity or skill to apply
  21. 21. 4.C Zinc Plating
  22. 22. Zinc Plating Zinc Plating is an electroplating process performed by using Zinc Sulphate solution. It is a low cost process making it feasible for smaller parts 4 C Purpose
  23. 23. Zinc Plating 4 C Process Cleaning Soak & Electro Cleaning Rinsing Plating Rinsing Bright Dip Chromate Coating and Rinsing Zinc Plated Part
  24. 24. Zinc Plating 4 C Types and Classes According to ASTM B-633: Classification Number Service Condition Thickness Fe/Zn 25 SC 4 (Very Severe) 25 Fe/Zn 12 SC 3 (Severe) 12 Fe/Zn 8 SC 2 (Moderate) 8 Fe/Zn 5 SC 1 (Mild) 5 Type I – Zinc, as plated Type II – Zinc, w/colored chromate Coating Type III – Zinc, w/colorless chromate Coating Type IV – Zinc, w/phosphate conversion Coating
  25. 25. Zinc Plating 4 C Process Tests Test Specimen Preparation Test method Coating Thickness Specimen Panels: (min length 100 mm, min width 25 mm, min thickness 1 mm) - B487, B499 Adhesion Specimen Panels: (min length 150 mm, min width 100 mm, min thickness 1 mm) - B571 Corrosion Resistance Specimen Panels: (min length 254 mm, min width 76.2, min thickness 0.02 in) - Salt Spray Test Hydrogen Embrittlem ent relief test Defined By Purchaser - Sustained Load of 75% of UTS
  26. 26. Zinc Plating 4 C Advantages • Chromate protected zinc offers higher corrosion resistance • The process is cheap • Electrolytic zinc coatings are used to protect and improve the appearance of ferrous metals, (i.e iron and steel) as a corrosion barrier, and then as a sacrificial coating
  27. 27. 4.D Cadmium Plating
  28. 28. Cadmium Plating Cadmium Plating is an electroplating process performed by using Cadmium cyanide solution 4 D Purpose
  29. 29. Cadmium Plating 4 D Process Degreasing Cleaning Soak Electro Ridoline Pickling Rinsing Cd Plating Process Rinsing Cd Plated Part
  30. 30. Cadmium Plating 4 D Types and Classes According to QQ-P-416 F: Types I – As plated II – Supplementary Chromate Coating III – Supplementary Phosphate Coating Classes 1 – 0.005 in minimum thickness 2 – 0.003 in minimum thickness 3 – 0.002 in minimum thickness
  31. 31. Cadmium Plating 4 D Process Tests Classes Minimum Thickness For external surface that can be touched by a ball 0.79 in in diameter For external surface that can not be touched by a ball 0.79 in in diameter Inch Microme ter Inch Micrometer 1 0.0050 18 0.00030 8 2 0.0030 8 0.00020 5 3 0.0020 5 0.00015 4
  32. 32. Cadmium Plating 4 D Advantages • Cadmium Plating is the preferred method of protecting close-tolerance steel parts against corrosion • It is particularly useful for reducing or avoiding bi-metallic corrosion and is suitable for soldering • Cadmium plating is liable to rapid attack by vapors emanating from certain woods, varnishes, plastics and other organic materials, particularly in poorly ventilated or humid conditions • This plating is mostly used on carbon steel and low alloy steel parts for protection against corrosion
  33. 33. 4.E Passivation
  34. 34. Passivation Passivation is a post plating process and is normally applied to cadmium and zinc plated parts and to zinc based alloy die-casted parts. Passivation process on plated surfaces reduces corrosion. 4 E Purpose
  35. 35. Passivation 4 E Process Clean/ Degrease Rinse Immersio n Rinse Immersio n Dry Passivated Part
  36. 36. Passivation 4 E Types and Classes According to QQ-P-35 C: Types I – Nitric Acid + Sodium Dichromate solution 70-90oF II – Nitric Acid + Sodium Dichromate solution 120-130oF III – Nitric Acid + Sodium Dichromate solution 145-155oF IV – For steels containing large amounts of sulfur or selenium (0.15%) V – Part Anodic at 3-5 V for high carbon martensitic (440) steels VI – Concentrated Nitric Acid solution 70-90oF VII – Concentrated Nitric Acid solution 120-140oF VIII – Concentrated Nitric Acid solution 120-130oF
  37. 37. Passivation 4 E Process Tests Test Test Specimen Test method Water Immersion Test The specimen shall consists of samples of parts that are submitted or selected for acceptance inspection. - MIL-STD-753B - Parts shall be cleaned with acetone - Parts then must be immersed in distilled water for 1 hour and allowed to dry for 24 hrs - No stains or rust must be visible High Humidity Test The specimen shall consists of samples of parts that are submitted or selected for acceptance inspection. - MIL-STD-753B - Parts shall be cleaned with acetone - Parts shall be subjected to 100% humidity at 100oF for 24 hours - No stains or rust must be visible Salt Spray Test The specimen shall consists of samples of parts that are submitted or selected for acceptance inspection. - Salt Spray Test for 2 hrs - ASTM B117 Copper Sulfate Test The specimen shall consists of samples of parts that are submitted or selected for acceptance inspection. - MIL-STD-753B - Parts shall be cleaned with acetone - Parts then must be swabbed with copper sulfate solution for 6 minutes - Parts must not show copper deposits
  38. 38. Passivation 4 E Advantages • Passivation process on plated surfaces reduces corrosion white rusting of cadmium and zinc under humid conditions • It helps to reduce the attack on both metals by certain vapors and organic substances • It improves the performances of subsequently applied parts • It can remove sulfides exposed on the surface of free-machining stainless alloys • It can remove surface contamination, such as particles of iron-containing shop dirt and iron particles from cutting tools that can form rust or act as initiation sites for corrosion
  39. 39. 4.F Phosphation
  40. 40. Phosphation Phosphation is a treatment process carried out on iron and steel to provide coatings for the protection of items against corrosion/rust or wear 4 F Purpose
  41. 41. Phosphation 4 F Types and Classes According to DOD-P-16232 F: I – Type M (Manganese Phosphate Base) Class 1 : Supplementary Preservative Treatment or Coating Class 2 : Supplementary Treatment with lubricating oil as per MIL-L-3150 Class 3 : No Supplementary Treatment Class 4 : Chemically converted with no supplementary treatment II – Type Z (Zinc Phosphate Base) Class 1 : Supplementary Preservative Treatment or Coating Class 2 : Supplementary Treatment with lubricating oil as per MIL-L-3150 Class 3 : No Supplementary Treatment Class 4 : Chemically converted with no supplementary treatment
  42. 42. Phosphation 4 F Process Tests Test Type Applicable Specimen Preparation Requirement Test method Coating Weight M & Z Specimen Panels: (10to 100 sq. cm with AQL 1.8 % defective) 3.6 - Weight Balance (Coating weight shall be 16 gm /m2 & 11 gm / m2 for M & Z type coatings respectively) Coating thickness M 0.005 to 0.010 mm 6.6 - Coating thickness gaugeZ 0.005 to 0.015 mm Corrosion Resistance M & Z Specimen Panels: (10 TO 100 Sq cm) 3.6, 4.7.5 - Salt spray test for 72 hours Surface Finish 6.5 - Surface tester (0.8 mm) Adhesion Resistance 6.5 - Grit size 320 or grade 1000 glass beads
  43. 43. Phosphation 4 F Process Tests Coating Type Material Hardness HRC (Minimum) Heat Treatment Stage of operation Z Alloy Steel Carbon Steel 39 39 98 to 107 degree for 8 hours or room temperature for 120 hours For both coatings Heat Treatment is carried out after coating but before any stressing operation M Alloy Steel Carbon Steel 39 39 Alloy Steel Carbon Steel 39 39 163 ± 14 degree for 4 hours or room temperature for 120 hours Stress relief shall be given to all parts having minimum hardness value of 39 HRC (Rockwell c)
  44. 44. Phosphation 4 F Process Tests Coating System E24xposure Time Minimum Type Class Salt Spray (Hours) Springfield Immersion Tests (Minutes) M 1 1-1/2 10 2 1-1/2 3 1-1/2 4 24 Z 1 2 2 2 3 2 4 24 Accelerated corrosion resistance requirements are as under:
  45. 45. Phosphation 4 F Advantages • Phosphation provides drastic protection of items against corrosion and wear & tear • It helps to reduce the attack on both metals by certain vapors and organic substances • It can remove surface contaminations, particles of iron-containing shop dirt and iron particles from cutting tools that can form rust or act as initiation sites for corrosion • It also gives anti-war properties to sliding surfaces during continuous running periods
  46. 46. M Bilal Khan Umer Farooq Saqlain Acknowledgements
  47. 47. References • MIL-A-8625 F • MIL-STD-171E • ASTM B-766-86 • MIL-C-5541C • MIL-DTL-16232G • DEF-DTD-904 • L-10205B • QQ-P-35 C • ASTM B-633 • DOD-P-16232F • Photos Taken from Flickr’s shares for commercial purpose. Special Thanks to the people who shared.

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