The most common standard for zinc plating is ASTM B633, which has four classifications for electroplated zinc. Each classification specifies which supplemental treatment or chromate to apply (Type I,II,III,IV,V, or VI) and the plating thickness according to the type of environment (SC1, SC2, SC3 or SC4).

ASTM B633-11 now addresses RoHS compliance.

Plating Thickness – The zinc plating shall be a minimum thickness of . 0002 inch (5 µm) on all significant surfaces. Surfaces on which the specified thickness of deposit cannot readily be controlled, such as threads, holes, deep recesses, bases of angles, and similar areas, are exempt from the thickness requirements.

The following briefly describes some of the common zinc colours/types:

• Zinc Gold Passivate. Yellow Zinc (Gold Zinc) is the most common type of zinc plating used in automotive parts finishing.
• Black Zinc.
• Blue or Clear Zinc.
• Zinc cobalt.
• Acid zinc.

about .0002”
Clear Zinc is often referred to as “commercial clear” or “commercial zinc” when an exact plating thickness is not specified. Commercial zinc plating provides coverage on all significant part surfaces with an approximate average coating thickness of about . 0002” – .

Yellow Zinc Plating refers to the color of the chromate that is applied after zinc has been deposited on to the surface of the part. Yellow chromate prevents the zinc from corroding and increases the overall protection of the finish. This finish provides a rainbow or iridescent appearance with dominant yellow tones.

The main difference is that zinc-plated steel is created using an electrical current, whereas galvanized steel is typically created using the hot-dip method. The hot-dip method lives up to its namesake by involving heated, molten zinc. The zinc particles are smelted in a furnace.

Zinc plating (also known as electro-galvanising) is a process where zinc is applied by using a current of electricity. While is does provide some rust protection, its thinner coating is not as rust resistant as hot dip galvanising. Its main advantage is it is cheaper and easier to weld.

Available colors are iridescent and black N633 chromate passivation gives corrosion resistance ability of 12 hours according to ASTM B until white spots-intended to parts used in a light corrosive environment —indoor. This standard has been approved for use by agencies of the Department of Defense.

The ASTM B633 Service Classes (e.g. ASTM B633 SC4) determine plating thickness as well as test requirements, so these SC designations should be used with or without specific thickness callouts added for clarity. & Chrome-Nickel-Copper on Iron, Steel, Copper & Zinc

ASTM B Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel. This specification covers requirements for electrodeposited. Colorful chromate passivation gives corrosion resistance ability of 96 hours according to ASTM B until white spots-intended to parts used in a high corrosive environment —outdoor.

For example, ASTM B633 Type I and ASTM B633 Type IV require no salt spray testing, while ASTM B633 Type II, ASTM B633 Type III, ASTM B633 Type V and ASTM B633 Type VI all require salt spray testing.