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

1. Surface
Finishing
Processes By Hassan Habib

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. What is surface finishing?
Surface Finishing is a set of processes that we use to achieve
desired mechanical properties on different products
1Purpose

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. 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. What is electroplating?
3Process
Anode
•Metal to
be plated
Cathode
•Part to be
plated
Sulphate
solution of
the same
metal
Electroplated
Part

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. 4.A
Anodizing

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. Anodizing 4
A
Process
Jigging
Degreasi
ng
Cleaning
Anodizin
g
Dyeing Sealing
Anodized
Part

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. • Bath Concentration = 10% H2SO4
• Current Density = 10-15 A/ft2
• Time = Depending upon requirement
• Temperature = 18oC-22oC
4
A
AnodizingProcess Specifications

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. 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. 4.B
Alodining

16. Alodining
Alodining is the chemical application of a
protective chromate conversion coating on
alumiunum
4
B
Purpose

17. Alodining 4
B
Process
Alkaline
Cleaning Rinsing
Deoxidati
on
Rinsing
Chromat
e Coating
Rinsing
Alodined
Part

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. 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. 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. 4.C
Zinc Plating

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. Zinc Plating 4
C
Process
Cleaning
Soak &
Electro
Cleaning
Rinsing Plating Rinsing
Bright
Dip
Chromate
Coating and
Rinsing
Zinc
Plated
Part

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. 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. 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. 4.D Cadmium
Plating

28. Cadmium Plating
Cadmium Plating is an electroplating process performed
by using Cadmium cyanide solution
4
D
Purpose

29. Cadmium Plating 4
D
Process
Degreasing
Cleaning
Soak
Electro
Ridoline
Pickling Rinsing
Cd
Plating
Process
Rinsing
Cd Plated
Part

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. 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. 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. 4.E
Passivation

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. Passivation 4
E
Process
Clean/
Degrease Rinse
Immersio
n
Rinse
Immersio
n
Dry
Passivated
Part

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. 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. 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. 4.F
Phosphation

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. 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. 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. 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. 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. 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. M Bilal
Khan
Umer
Farooq
Saqlain
Acknowledgements

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.