| Hard Anodize | Sulfuric Anodize | Black Oxide Coating | Chemical Films | Chrome |
| Electroless Nickel | Electropolishing | Gold | Nickel | Passivate | Phosphate Coating | Tin | Zinc |

Hard Anodize

Coating PENETRATES base metal as much as builds up on the surface.  The term thickness includes both the buildup and penetration.  Color will vary from light tan to black depending on alloy grade and finish thickness.  Hard anodize can be dyed in darker colors depending on finish thickness.  It provides very hard ceramic type coating.  Abrasion resistance will vary with alloy and thickness of coating.  Good dielectric properties.  Corrosion resistance is good, but recommend seal hard anodize in 5% dichromate solution where increased corrosion resistance is required.  Where extreme abrasion resistance is required, do not seal as some softening is encountered.

MIL-A-8625E RoHS Compliant

Type III

.0005 - .0045" or as specified on drawing

If not specified, thickness shall be .002 ± .0005"

Can be used on most Aluminum alloys depending on process used.  Thick coatings (over .004") will tend to break down sharp edges.

Typical applications:

·    Hydraulic cylinders, wear surfaces, actuating cams, etc.

·    Electrical insulation coating

“FLASH” hard anodize may be used instead of conventional anodize for corrosion resistance and may be more economical in conjunction with other hard anodized areas.  Where maximum serviceability or special properties are required, consult metal finisher for best alloy choice.

Class 1

 

Non-Dyed

Class 2

 

Dyed

Sulfuric Anodize

Color will vary with alloy.  Aluminum with low alloying elements will show practically no color change.  Best coating on aluminum for dyeing.  Sulfuric anodize can be dyed practically any color or shade (black, blue, red, metallic, etc.).  Salt spray requirement is 336 hours (5% solution per method 811 of FED-STD No. 151.

MIL-A-8625E RoHS Compliant

Type II

.00005 - .0010"

All aluminum alloys, but do not use where solution will be entrapped.

FED-STD No. 595 may be used as a guide for specifying color (approximate comparison only.)

Class 1

 

Non-dyed

Minimum weight — 600 mg. / sq. ft.

Class 2

 

Dyed

Minimum weight — 2,500 mg. / sq. ft.

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Black Oxide Coating

Black oxide is a uniform decorative black coating for ferrous metals.  It has only very limited corrosion protection under mild corrosion conditions.

Black oxide coatings should normally be given a supplementary treatment (i.e. oil displacement per MIL-C-16173 Grade 3).

MIL-C-13924C RoHS Compliant

 

No Dimensional Change

For moving parts which cannot tolerate the dimensional change for a more corrosion resistant finish.  For decorative applications and can be used to decrease light reflection.

Class 1

 

Alkaline oxidizing.

For wrought iron, plain carbon, and low alloy steels.

Class 3

 

Fused salt oxidizing.

For steels having draw temperatures above 900◦ F.

Class 4

 

Alkaline oxidizing.

For corrosion resistant steels.


Chemical Films

Chemical film is a coating for aluminum.  Color can vary from colorless to golden-iridescent-brown.  Coatings shall be continuous, free from powdery areas, breaks, scratches, etc.


Salt-Spray Test - (unpainted surfaces)


Treatment


Aluminum Alloy

Exposure
to Salt Spray

Class 1A

2024-T3

168 Hours

Class 3

6061-T6

168 Hours

 

6063-T6

 
 

7074-T6

 

MIL-C-5541E RoHS Compliant Clear Chem Film Only

 

No Dimensional Change

Used mainly as a base for paint, and where conductivity and corrosion resistance is required.  Also used for touch-up, where rework has removed anodize.  NOTE:  Abrasion resistance is poor.

Class 1A

 

For maximum protection against corrosion, painted or unpainted.

Class 2

 

For protection against corrosion where low electrical resistance is required.


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Chrome

Chrome has excellent hardness (Rc68-74) for wear resistance and erosion.  It is low coefficient of friction, and is resistant to heat.  Chrome can be made porous for lubrication purposes.


QQ-C-320B RoHS Compliant

Type I

 

Bright finish (high polish)

 

Type II

 

Satin finish (matte finish)

 

Class 1

.00001 - .00002"

Decorative plating (usually over copper and nickel plated undercoats).

 

Class 2

As specified on drawing

Engineering plating.

 

Class 2a

Plated to specified dimension or process to specified dimensions after plating.

Post bake at 375◦ ±  25F for 3 hours or as specified

Class 2b

Parts below Rockwell C40 and subject to static loads or designed for limited life under dynamic loads.

Shot peening and post baking not required.

Class 2c

Parts below Rockwell C40 and designed for unlimited life under dynamic loads.

Shot peen per MIL-S-13165

Class 2d

Parts have hardness of Rockwell C40 or above and subject to static loads or designed for limited life under dynamic loads.  Applies to Class 2d and 2e.

Post bake at 375◦ ± 25F for 3 hours.

Class 2e

Shot peen before plating.  Post bake at 375◦ ± 25F for 3 hours.


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Electroless Nickel

Electroless nickel is similar to stainless steel in color.  It plates uniformly in recesses and cavities.  It doesn’t build up on edges.  Corrosion resistance is good for coatings over .001" thickness.  In the as-plated condition, electroless nickel has a hardness of Rc46 to Rc50.

Heat treating for 1 hour at 700F will increase hardness to Rc62 to Rc67.  Class 2 coatings shall have a minimum hardness of 700 Vickers.  As a relatively hard coating, is unique in that it has a high lubricity characteristic.  On ferrous alloys with hardness of Rc40 or greater requires a post bake at 375◦ ± 25F for 3 hours.


MIL-C-26074D RoHS Compliant

Grade A

Unless otherwise specified
.0010"

 

Grade B

.0005"

 

Grade C

.0015"

 

Class 1

 

As plated for decorative use and corrosion protection.

Class 2

 

Heat treated to obtain required hardness.

Class 3

 

Aluminum alloys, non-heat treatable.  Beryllium alloys process to improve corrosion of the nickel deposit.

Class 4

 

Aluminum alloys, heat-treatable, improves adhesion to nickel deposit.


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Electropolishing

Process electrolytically removes or diminishes scratches, burrs and unwanted sharp edges from most metals.  Finishes from satin to mirror-bright are produced by controlling time, temperature, or both.

NO MIL SPEC RoHS Compliant

 

.0002

Typical dimensional change.  Process is not recommended for close tolerance surfaces.


Gold

Yellow to orange color depending on proprietary process used.  Color will range from matte to bright finish depending on basis metal.  Good corrosion resistance, and has high tarnish resistance.  Soft 24K gold will have a hardness of about 90 knoop.  Hard 23K gold will have a hardness of up to 300 knoop.  Provides a low contact resistance, and is a good conductor.

MIL-G-45204C RoHS Compliant

Type I

99.0%

Most industrial applications.

Type II

99.7%

Hard plate where wear is important.

Type III

99.9%

Electronic applications.

Class 00

.00002"

Gold flash — decorative

Class 0

.00003"

Gold flash — decorative

Class 1

.00005"

Over silver underplate

Class 2

.00010"

Waveguides, contacts non-migratory

Class 3

.00020"

Std thickness for engineering use.

Class 4

.00030"

For exceptional corrosion and wear.

Class 5

.00050"

For exceptional corrosion and wear.

Class 6

.00150"

For Cathode emission characteristics.

Grade A

 

Knoop hardness 90 max

Grade B

 

Knoop hardness 91 — 129 inclusive

Grade C

 

Knopp hardness 130 — 200 inclusive

Grade D

 

Knoop hardness 201 — over


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Nickel

Nickel can be deposited soft or hard, dull or bright, depending on the process used and condition employed in plating.  Thus hardness ranges from 150 — 500 Vickers.  It can be similar to stainless steel in color, or can be a dull gray or light white gray color.  Corrosion resistance is a function of thickness.  Low coefficient of thermal expansion and is not magnetic.  All steel parts having a hardness of Rc40 or greater require a post bake of 375 ± 25F for 3 hours.


QQ-N-290A RoHS Compliant

Class 1

Total thickness of nickel

For decorative applications on steels, zinc and zinc alloys, copper and copper alloys.

Grade A

.0016"

1.Steels require a .0002" minimum copper underplate.

2.Zinc and zinc alloys shall have an underplate of .0002" minimum.

3.Copper alloys containing 40% or more zinc require a copper underplate of .0003" minimum.

Grade B

.0012"

Grade C

.0010"

Grade D

.0008"

Grade E

.0006"

Grade F

.0004"

Grade G

.0002"

Class 2

 

As specified for engineering application.


Passivate

A process designed to remove foreign metals from the surface of stainless and corrosion resistant steels and to promote natural tendency of surface to oxidize.  It does not change the appearance of the base metal.  Process purifies and therefore improves corrosion resistance.

QQ-P-35 RoHS Compliant

 

No Dimensional Change

Some so called corrosion resistant alloys (i.e., AM355, 350, Ph 17-4, 17-7 and 15.7Mo) are not always stable as far as corrosion resistance is concerned (depending upon the heat treat condition).  It should also be noted that if heat treating is performed in an oxidizing atmosphere, the 400 series exhibits different characteristics when passivated, and can result in light rusting shortly after passivating.  In many cases, fabricators have resorted to Cadmium plating, nickel plating, or oiling of 400 series to prevent rusting.


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Phosphate Coating (Light)

Specification covers cleaning methods and pretreatment process.  Light coating for use as paint base.

TT-C-490C

Type I

Intended as a general all purpose pretreatment prior to plating.

Type II

Intended primarily for use where metal parts are to be formed after painting.

Type III

Intended for use where size and shape preclude using Type I and Type II metal components are assembled prior to treatment.


Cleaning Methods

Pretreatment Methods

Method I

Mechanical or abrasive cleaning

Type I

Zinc phosphate

Method II

Solvent cleaning

Type II

Iron phosphate

Method IIII

Hot alkaline

Type III

Organic pre-treatment coating (wash primer)

Method IV

Emulsion

Type IV

Non-aqueous iron phosphate

Method V

Alkaline derusting

Type V

Zinc phosphate

Method VI

Phosphoric acid

   

Phosphate Coating (Heavy)

Type Z can be used up to 200F to prevent galling in extrusion and deep drawing Class 2 is good for corrosion resistance.

DOD-P-16232F

   

Heavy coating for corrosion and wear resistance.

Type Z

 

Zinc phosphate base coating (1000 mg. / sq. ft.)

Class 1

 

Supplementary preservative oil treatment as specified

Class 2

 

Supplementary treatment with preservative conforming to MIL-PRF-1617", Grade "or MIL-PRF-3150

Class 3

 

No supplementary treatment

Class 4

 

Chemically converted (may be dyed to color as specified) with no supplementary coating or coating as specified


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Tin

Color is gray-white in a plated condition.  It has a very high luster in fused condition.  Soft, but is very ductile.  Corrosion resistance is good.  (Coated items should meet 24 hour 20% salt spray requirement.)  Solderability is excellent.  Tin is not good for low temperature applications, (changes structure and loses adhesion when exposed to temperature below -40F).

If a bright finish is desired to be used in lieu of fused time, specify Bright Tin plate.  Thickness can exceed that of fused tin and deposit shows excellent corrosion resistance and solderability.

MIL-T-10727A RoHS Compliant

Type I

As specified on drawing.  Thickness Guide: (not part of MIL spec)

Electrodeposited

Type II

Hot dipped

 

.0001 - .00025"

Flash for soldering

 

.0002 - .0004"

To prevent galling and seizing

 

.0003" minimum

Corrosion resistant

 

.0002 - .0006"

Prevents formation of case during nitriding


Zinc

Either a bright or dull finish is acceptable. Bright zinc plating closely resembles bright chromium. However, bright zinc does not have the permanence for surface appearance. Zinc coated steel will not rust even when exposed by scratches because of the galvanic protection of the zinc. Upon weathering, zinc turns to a drab gray color. Zinc should be deposited directly on the base metal (nickel is permissible undercoat if base metal is a corrosion resisting steel). Parts having a hardness greater than Rc-40 must be baked after plating at 375 ± 25F for 3 hours minimum. Baking must be done within 4 hours of plating. This must be specified by the purchaser.

ASTM-B633-85 RoHS Compliant

FE/ZN 25

.0010"

Primary use of chromate finishes on zinc is to retard or prevent formation of white corrosion products on zinc surfaces.

FE/ZN 12

.0005"

FE/ZN 8

.0003"

FE/ZN 5

.0002"

Type I

 

As plated no supplementary treatment

Type II *(Not RoHS Compliant)

 

Colored chromate conversion coatings

Type III

 

Colorless chromate conversion coating

Type IV

 

Phosphate conversion coatings.  Primary purpose of phosphate coating on zinc is to provide a paint base.

| Hard Anodize | Sulfuric Anodize | Black Oxide Coating | Chemical Films | Chrome |
| Electroless Nickel | Electropolishing | Gold | Nickel | Passivate | Phosphate Coating | Tin | Zinc |

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