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Chrome flaking from large hydraulic piston

2005

Hello All,

Recently I began working on a large hydraulic piston for a large press to repair an area that has chrome flaking. The piston is 45" OD x 130" Long and approx. 45,000# and has Chrome Plating about .020" thick. The part was pre-ground, grit blasted, rotary plated, and post-plate ground to size. In my experience if there was an adhesion problem the chrome would have flaked during the post-grind process. The plater's suggestion there was damage during the assembly process which has caused the chrome to crack in areas and therefore lose its adhesion. My issue with this response is that we have seen the flaking in areas with no visual damage (including 100X with scope), there were a few areas that showed a checking pattern which I could understand may have been damaged during assembly. We fixed these spots with a chrome over chrome process, but as I stated other areas in the same general area are no starting to flake. Flake approx. 1/2" wide x 2" long. General areas of defects is limited to an area approx. 24" x 24".

Application - Part is moving up and down through a bronze bushing and a seal, lubrication is hydraulic fluid.

Any suggestions on what else might be causing the chrome to flake?

John E Coward
Industrial Engineer - Spring Grove, Illinois, USA

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I's not possible to eliminate a true plating problem, but from the description, I'd guess the problem was caused in the post plate grinding - too aggressive. feed, wrong coolant, etc.

Jeffrey Holmes, CEF
Spartanburg, South Carolina
2005