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Hard Chrome Plating on Cast Irons containing Graphite

We are facing a problem while Hard Chrome Plating on Cast Irons containing Graphite, the chrome simply does not adhere, even after 3.25 Amp/square inch.We are considering Grit Blasting or undercoat plating?

Neil Paarekh
- Mumbai, Maharashtra, India

Neil,

We had similar problems plating chrome onto graphite cast iron, specifically meehanite gray cast iron. The problem was resolved by grit blasting as you mentioned, then going into the chrome tank "live", with both anode and cathode connected, and current on at about 6 volts. (We use welding cable as temporary jumpers when going into tank live.) You will need to "strike" with about 6-8 amps/sq. in., then process at approx. 3 amps/sq. in. Another important factor is to process as soon as possible after grit blast (before the metal oxidizes too much).

Ralph Peltier
- Providence, Rhode Island

Q. Possibility of safely making hard chrome plate on cast iron rolls fi 400mm.
Quality: ASTM Gr.45-12 (normalized and tempered)- 3,5%C; 2,6%Si...0, 3-0, 4%Mg
Influence of free graphite?

Jakob Habjan
engineer, metalurgist - Celje, Slovenia
December 21, 2011

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