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Chrome Coating Over Cast Steel

I am thinking of chrome coating (.005 - .007 in thk) a cast steel (not sure the exact grade) pump housing. The pump operates at 450 F and I am wondering the thermal expansion properties will cause one to grow faster than the other creating cracks or other weaknesses in the coating? Is there another sort of coating I should try?

Whit Wood
Maintenance Engineer - Pasadena, Texas, USA
February 9, 2011

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Most castings are miserable to plate. 0.007" per side is a rather thick coating and you may see larger than the normal micro cracking. I would look at copper-nickel-nickel chrome, ala truck bumpers only a bit thicker chrome than they use.

0.002 of electroless nickel would be worth trying or beta testing.

Depending on the exact steel that you use, thermal expansion may or may not be a problem.

James Watts
- Navarre, Florida
First of two simultaneous responses -- February 10, 2011

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Heavy duty cast diesel crankshafts are salvaged by plating .030" chrome and more every day of the week.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
Second of two simultaneous responses -- February 10, 2011

I agree with James. Crankshafts are indeed chromed but only on their journals which are uniform and thoroughly machined to a sound and clean surface. Castings like pump housings, besides their natural contaminated, porous and rough surface also present an irregular geometry not suitable for electroplating, especially chrome. Why are you looking for chrome. Is it erosion or corrosion? What is the fluid, temperature is too high for water or water based solutions. G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
February 13, 2011