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Relative merits of steel finishing

I'm looking for the best method to finish a small steel fabrication. The criteria in order are:

1. Cheap
2. Good Electrical Conductivity
3. Good Corrosion Resistance

Can somebody suggest whether I should use Nickel Plating/Zinc Phosphate or whatever.

John Darrington
- Perth, WA, Australia
2002

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2003

Hi John,

First contact local jobshops for available processes and minimum prices. Factors that affect processing and pricing: Quantity, size, material (CRS, galvanized,Â), welded (continuous or with gaps allowing liquid into seams, burns, splatter) or bolted (disassemble), cavities, blind holes, masking, tight tolerances, etc. In order of increasing cost, some basic options are:

1) Zinc plating + chromate (clear/blue for better conductivity, yellow for corrosion resistance).
2) Nickel electroplating (ask if duplex plating is available).
3) Nickel electroplating with a copper underplate.
4) Electroless nickel (for corrosion resistance, high phos > mid-phos > low phos).

Of course, both corrosion resistance and cost increase with plating thickness. Phosphating + painting offers cost-effective corrosion protection, but lacks electrical conductivity. If only a few electrical contacts are needed, zinc plate + chromate, then mask or plug the contact areas and paint. Paint options are numerous; powder coat is good, but a small volume of parts may not justify. If you do your own painting, use polyurethane over (or instead of) epoxy for sunlight exposure.

Ken Vlach [deceased]
- Goleta, California
Finishing.com honored Ken for his countless carefully researched responses. He passed away May 14, 2015.
Rest in peace, Ken. Thank you for your hard work which the finishing world, and we at finishing.com, continue to benefit from.

Would Black oxide (bluing or blackening) provide these criteria in this order? It is about as cheap as phosphating (similar process and in the same mil spec), but doesn't actually plate the steel so it maintains most of its electrical conductivity. And the last criteria of corrosion resistance would be achieved with the appropriate post treatment. The final answer depends on the actual use of the parts though.

Justin Martin
Liverpool, Pennsylvania, USA
2003