Metal finishing Q&As since 1989

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General-Purpose Plating for Industrial Fasteners?

2003

My electronics company is tired of buying whatever is available at the local hardware store, and wants to get serious about specifying fasteners via tab drawings. The equipment we manufacture is sold to telephone companies who generally store the units in air-conditioned indoor environments. Most of our applications involve fastening pc boards and sub-assemblies to stamped steel frames. A basic question is whether to specify (passivated) stainless steel fasteners or (zinc ?) plated steel. I'm looking for opinions on this. If plated steel, what is a good general-purpose plating/coating ? Lastly, we may require a black plating/coating for aesthetic purposes. What is best - black zinc, or black oxide, or something else ? Our company has design and assembly plants in several countries so we want to specify a fastener plating that is readily available everywhere and is referenced in ISO or National specifications. We also need to tie down the plating of equipment steel frames and racks. What is a good callout for this purpose ?

Kalos Orisate
- Christchurch, New Zealand

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For a black finish zinc or zinc iron and a black conversion coating will be more than adequate. The zinc iron will enable you to have higher corrosion resistance. If your equipment is exported to Europe, you should look into the idea of having products specified as hexavalent chromate free. There are a variety of trivalent chromate films available for zinc and zinc alloy plating which will give excellent corrosion protection.

Stainless steel would be fine except that it is costly and is generally not available in black.

Gene Packman
process supplier - Great Neck, New York
2003