Example of Zinc Plated Part With Yellow Chromate

Zinc Plating

Electroplated zinc protects steel, cast iron, malleable iron, copper, and brass from destructive corrosion. The zinc chemically bonds to the part surface and functions as a "sacrificial coating", corroding before the base material but in the process greatly extending part life. To increase the corrosion protection Chem Processing Inc. offers RoHS compliant clear trivalent chromium and yellow trivalent chromium seals, as well as yellow dichromate and olive drab hexavalent chrome-based seals. Chem Processing, Inc. also offers a range of inorganic and organic topcoats, such as Doerken Delta Seal, that can significantly enhance the corrosion protection offered by zinc plating. Contact CPI for more on these options. Chem Processing, Inc. offers olive drab chromate conversion coating as a post-plate treatment for military applications.

Zinc is an efficient, economical coating, with a minimal environmental impact. Plated zinc is not recommended for equipment that is continually immersed in solutions, petroleum applications, pharmaceutical applications, or food-handling applications. Zinc should not be used in vacuum (spaceflight) applications (see NASA prohibition ). It is also not recommended for aerospace applications (per AMS 2402). Plated zinc deposits treated with a hexavalent chromate conversion coating should not be subjected to temperatures above 140F for prolonged periods as this will dehydrate the chromate film and greatly reduce the corrosion protection it provides1. 

Chem Processing Inc. Zinc Plating Capabilities:

  • Plating thickness range of 0.0001 to 0.002 in.
  • Acid chloride and alkaline plating chemistries to optimize finish characteristics
  • Precision rack processing
  • Bulk barrel processing
  • Precision masking
  • Post-plate hydrogen embrittlement relief thermal treatment
  • RoHS compliant clear, yellow and black post-plate treatments
  • Clear, yellow, black and olive drab chromate treatments
  • Post-plate/post-chromate seals/topcoats for enhanced corrosion protection
  • XRF thickness analysis

Applicable Specifications:

  • ASTM B633
  • AMS 2402
  • MIL-STD-171
  • QQ-Z-325

Typical Salt Spray (ASTM B117) Results:

Finish (0.0005") / Hours Until Red Rust

Zinc / 12
Zinc w/ Clear Trivalent Chromate / 336
Zinc w/ Clear Hexavalent Chromate / 96
Zinc w/ Yellow Trivalent Chromate / 336
Zinc w/ Yellow Hexavalent Chromate / 240
Zinc w/ Black Hexavalent Chromate / 300+
Zinc w/ Olive Drab Hexavalent Chromate / 400+
Zinc w/ Clear Hexavalent Chromate & Seal / 240

Chem Processing Inc. offers precision rack and barrel zinc plating services to Illinois, Wisconsin, Iowa, the Midwest and beyond. CPI is strategically located by highway routes to Chicago, Milwaukee, Madison, St. Louis, and Minneapolis. The CPI facility is minutes from a major Midwestern air freight hub , enabling efficient door-to-door delivery across the United States or across the globe.

1: Geduld, H. Zinc Plating. ASM International. Metals Park, OH. 1988