52030

Hard chromium plating of magnesium  

April 29, 2009

I have some machined magnesium parts that have a critical ID that was machined oversize. We're considering having the ID's hard chromium plated and then grinding them to size. Is this possible? I'm not sure if the magnesium is compatible with the hard chromium bath/process. If it is, then is there a special process that should be followed to accomplish our needs?

Blaine B. Boyd
customer - Eastlake, OH, USA

Whatever you do, it needs the blessing of the customer before you spend money on the fix.
If it is less than 0.003" on the diameter (0.0015" per side), I would choose EN because it is very uniform and would require little or no grinding. For chrome, I would not use less than 0.015 per side as your grinding setup needs to be nearly flawless in alignment to the original grind. Chrome dog bones on the ends and you will have quite a bit of grinding to do. Your grinders must be familiar with grinding chrome or they will use the wrong wheel or take too deep cuts and the chrome will probably peel.

James Watts
- FL

Depending on the overall geometry of the part, how much metal you need to build-up and what your tolerances are, it might be possible to selectively brush plate that ID, perhaps even do it to size as-plated (no grinding or machining). The process is versatile and permits the deposition of a variety of metals whose chemical and mechanical properties can be selected to match or come closer to those of your base metal.

Guillermo Marrufo
Monterrey, NL, Mexico