| Finish or Coating | Used On | Corrosion Resistance | Characteristics |
|---|---|---|---|
| Anodizing | Aluminum | Excellent | Acid electrolytic treatment for aluminum, frostyetched appearance. Hard oxide surface gives excellent protection. |
| Black oxide, blued | Steel | Indoor satisfactory, outdoor poor. Protection afforded mainly by wax or oil coatings | Hot-alkali chemical process, black, can be waxed or oiled. Produces a rust-inhibited surface. |
| Black chromate | Zinc-plated or cadmium-plated steel | Added corrosion protection on cadmium and zinc-plated surfaces | Black, semilustrous. Chemical dip. Used for decorative outdoor purposes. Can be lacquered. |
| Blueing | Steel | Indoor satisfactory, outdoor poor. Protection afforded mainly by wax or oil coatings. | Coloring process by heat tinting. Decorative use. Blue to black, can be waxed or oiled. |
| Brass plate, lacquered | Steel, usually | Fair | Brass electroplated finish which is then lacquered. Recommended only for indoor decorative use. |
| Bronze plate, lacquered | Steel, usually | Fair | Has color similar to 80% copper, 20% zinc alloy. Electroplated, lacquered finish. Only recommended for indoor decorative use. |
| Cadmium plate | Most metals | Very good | Bright silver-gray, dull gray or black electroplated finish. Used for both decoration and corrosion protection. |
| Clear chromate finish | Cadmium and zinc-plated parts | Very good to excellent | Clear bright or iridescent chemical conversion coating applied to zinc or cadmium-plated surfaces for added corrosion protection, coloring, and paint bonding. The colored coatings usually have greater corrosion resistance than the clear. |
| Dichromate | Cadmium and zinc plated parts | Very good to excellent | Yellow, brown, green, or iridescent colored coating same as clear chromate. |
| Olive drab, gold, or bronze chromate | Cadmium and zinc-plated parts | Very good to excellent | Green, gold or bronze tones same as clear chromate. |
| Chromium plate | Most metals | Good (improves with increased copper and nickel undercoats) | Bright blue-white, lustrous electroplated finish. Has relatively hard surface. Used for decorative purposes. |
| Copper plate | Most metals | Fair | Electroplated finish. Used for nickel and chromium-plate undercoat. Can be blackened and relieved to obtain Antique, Statuary, and Venetian finishes. |
| Cooper, brass, bronze misc. finishes | Most metals | Indoor, very good | Decorative finishes. Applied to copper, brass, bronze-plated parts to match colors. Color and tones vary from black to almost the original color. Finish names are: Antique, Black Oxide, Statuary, Old English, Venetian, Cooper Oxidized. |
| Lacquering, clear or color-matched | All metals | Improves corrosion resistance. Some types designed for humid or other severe applications | Used for decorative finishes. Clear or colored to match mating color or luster. |
| Lead-tin | Steel, usually | Fair to good | Silver-gray, dull coating. Gives good lubrication to tapping screws. Applied by hot-dip method. |
| Bright nickel | Most metals | Indoor excellent. Outdoor good if thickness is at least 0.0005 in. | Electroplated silver finish. Used for appliances, hardware, etc. |
| Dull nickel | Most metals | Same as bright nickel | Whitish cast. Can be obtained by mechanical surface finishing or using a special plating bath. |
| Passivating | Stainless steel | Excellent | Chemical treatment. Removes iron particles and produces a passive surface. |
| Phosphate Bearing Surfaces, Army 57-0-2, Type II, Class A | Steel | Good | Antichafing properties used on sliding or bearing surfaces. Black manganese-iron phosphate coating with nondrying petroleum oils containing corrosion inhibitors. |
| Phosphate Rust Preventive, Army 57-0-2, Type II, Class B | Steel | Fair to good | Chemical process that rustproofs steel. Plain grayish surface. Rust-preventive oils can be applied over it. Can be dyed black. The rust-preventive oils increase corrosion resistance. |
| Phosphate, Paint-base Preparations, Army 57-0-2, Type II Class C | Steel, aluminum, zinc plate | Good, after paint or lacquer applications | Plain gray color. Chemical process for preparing steel, aluminum, and zinc-plated parts for painting or lacquering. Will increase bond between metal and coating. |
| Colored phosphate coatings | Steel | Superior to regular phosphated and oiled surfaces | Chemically produced color coating will increase corrosion resistance. Available in green, red, purple, blue, black, etc. |
| Rust preventatives | All metals | Varies with function of oil | Vary in color, and film thickness. Usually applied to phosphate and black oxide finishes. Used to protect parts in transit or prolonged storage. |
| Silver plate | All metals | Excellent | Decorative, expensive. Excellent electrical conductor. |
| Electroplated tin | All metals | Excellent | Silver-gray color. Excellent corrosion protection for parts in contact with food. |
| Hot-dip tin | All metals | Excellent | Silver-gray color. Same as electroplated, but thickness is harder to control, especially on fine-thread parts. |
| Electroplated zinc | All metals | Very good | Bright-blue-white gray coating. For corrosion protection of steel parts. |
| Electrogalvanized zinc | All metals | Very good | Use where bright appearance is not wanted. Dull grayish color. |
| Hot-dip zinc | All metals | Very good | For maximum corrosion protection. Dull grayish color. Use where coating thickness is not important. Corrosion resistance is directly proportional to the coating thickness. |
| Hot-dip aluminum | Steel | Very good | For maximum corrosion protection. Dull grayish color. Use where coating thickness is not important. Corrosion resistance is directly proportional to the coating thickness. |