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Thin Dense Chrome - Still a galvanic corrosion risk? Other options for gear teeth?

January 26, 2011

I am trying to decide on the best way to build steel gears, shafts and threaded components which will be subject to periodic submersion in fresh (not salt) water. I figure I have three options

1) Build the parts from Nitronic 60 or other gall resistant stainless alloy. For the gears this means a reasonably expensive custom hobbing operation.

2) Use commercial steel gears and apply a "thin dense chrome" ("Magnaplate Dynaloy") plating. Might be cheaper and faster, but I'm worried about galvanic corrosion between the chrome and the steel gears or stainless shafts. I don't know if this is a problem with TDCs as it is with hard chrome

3) Use commercial steel gears and apply some other coating. I evaluated Electroless Nickel on a previous job, but found that it had to be applied too thickly to work well on some of our precision shaft/bore fits. I'm not sure if the same would apply to gear teeth or threads, or if the adhesion is adequate for this application. Are there any other candidate coatings?

Brendan Simons
Design Engineer - Hamilton, Ontario