surface finishing processes - electroplating
TRANSCRIPT
Surface Finishing Processe
sBy Hassan Habib
Table of Contents
1.2.3.4.4.A4.B4.C4.D4.E4.F
What is surface finishing?
What is Electroplating?
Anodizing
Zinc Plating
Phosphating
Why we use electroplating?
Types of electroplating?
Alodining
Cadmium Plating
Passivation
What is surface finishing?
Surface Finishing is a set of processes that we use to achieve desired mechanical properties on
different products
1Purpose
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
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
What is electroplating? 3Process
Anode• Metal to be plated
Cathode
• Part to be plated
Sulphate solution of the same metal
Electroplated Part
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
4.A Anodizin
g
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
4A
Purpose
Anodizing 4A
Process
Jigging Degreasing
Cleaning
Anodizing Dyeing Sealing Anodize
d Part
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
4A
AnodizingTypes and Classes
• Bath Concentration = 10% H2SO4
• Current Density = 10-15 A/ft2
• Time = Depending upon
requirement
• Temperature = 18oC-22oC
4A
AnodizingProcess Specifications
4A
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)
3.7.1.13.7.2.1.1
- 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.
4A
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
4.B Alodining
Alodining
Alodining is the chemical application of a protective chromate conversion coating
on alumiunum
4B
Purpose
Alodining 4B
Process
Alkaline
Cleaning
RinsingDeoxidation Rinsing
Chromate
CoatingRinsing Alodined
Part
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.
4B
AlodiningClasses
4B
AlodiningProcess Tests
Test ClassApplicable
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
4B
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
4.C Zinc
Plating
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
4C
Purpose
Zinc Plating 4C
Process
CleaningSoak & Electro
CleaningRinsing Plating Rinsing Bright
Dip
Chromate Coating
and Rinsing
Zinc Plated Part
Zinc Plating 4C
Types and Classes
According to ASTM B-633:
Classification Number Service ConditionThickness
Fe/Zn 25 SC 4 (Very Severe) 25Fe/Zn 12 SC 3 (Severe) 12Fe/Zn 8 SC 2 (Moderate)
8Fe/Zn 5 SC 1 (Mild) 5
Type I – Zinc, as platedType II – Zinc, w/colored chromate CoatingType III – Zinc, w/colorless chromate CoatingType IV – Zinc, w/phosphate conversion Coating
Zinc Plating 4C
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 Embrittlement relief
test
Defined By Purchaser - Sustained Load of 75% of UTS
Zinc Plating 4C
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
4.D Cadmium Plating
Cadmium Plating
Cadmium Plating is an electroplating process performed by using Cadmium cyanide solution
4D
Purpose
Cadmium Plating 4D
Process
Degreasing
CleaningSoak
ElectroRidoline
Pickling Rinsing
Cd Plating Proces
sRinsing
Cd Plated Part
Cadmium Plating 4D
Types and Classes
According to QQ-P-416 F:
TypesI – As platedII – Supplementary Chromate CoatingIII – Supplementary Phosphate Coating
Classes1 – 0.005 in minimum thickness2 – 0.003 in minimum thickness3 – 0.002 in minimum thickness
Cadmium Plating 4D
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 Micrometer
Inch Micrometer
1 0.0050 18 0.00030 82 0.0030 8 0.00020 53 0.0020 5 0.00015 4
Cadmium Plating 4D
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
4.E Passivation
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.
4E
Purpose
Passivation 4E
Process
Clean/Degrease Rinse
Immersion Rinse Immers
ion Dry Passivated Part
Passivation 4E
Types and Classes
According to QQ-P-35 C:
TypesI – Nitric Acid + Sodium Dichromate solution 70-90oFII – Nitric Acid + Sodium Dichromate solution 120-130oFIII – Nitric Acid + Sodium Dichromate solution 145-155oFIV – For steels containing large amounts of sulfur or selenium (0.15%)V – Part Anodic at 3-5 V for high carbon martensitic (440) steelsVI – Concentrated Nitric Acid solution 70-90oFVII – Concentrated Nitric Acid solution 120-140oFVIII – Concentrated Nitric Acid solution 120-130oF
Passivation 4E
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
Passivation 4E
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
4.F Phosphatio
n
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
4F
Purpose
Phosphation 4F
Types and Classes
According to DOD-P-16232 F:
I – Type M (Manganese Phosphate Base)Class 1 : Supplementary Preservative Treatment or CoatingClass 2 : Supplementary Treatment with lubricating oil as per MIL-L-3150Class 3 : No Supplementary TreatmentClass 4 : Chemically converted with no supplementary treatment
II – Type Z (Zinc Phosphate Base)Class 1 : Supplementary Preservative Treatment or CoatingClass 2 : Supplementary Treatment with lubricating oil as per MIL-L-3150Class 3 : No Supplementary TreatmentClass 4 : Chemically converted with no supplementary treatment
Phosphation 4F
Process Tests
Test TypeApplicable 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 mm6.6 - 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
Phosphation 4F
Process Tests
Coating Type Material
HardnessHRC
(Minimum)Heat Treatment Stage of
operation
Z Alloy SteelCarbon Steel
3939
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 SteelCarbon Steel
3939
Alloy SteelCarbon Steel
3939
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)
Phosphation 4F
Process Tests
Coating System E24xposure Time Minimum
Type Class Salt Spray (Hours)
Springfield Immersion
Tests(Minutes)
M
1 1-1/2
10
2 1-1/23 1-1/24 24
Z1 22 23 24 24
Accelerated corrosion resistance requirements are as under:
Phosphation 4F
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
M Bilal Khan
Umer Farooq
Saqlain
Acknowledgements
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.