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Best plating for mild steel semi-trailer parts?

October 25, 2010

We are an over the road semi trailer manufacture based in Iowa. Our winters can be somewhat harsh especially when the DOT puts down the salt mix for the icy roads. I have a door shaft (picture attached) that I have plated with clear Zinc chromate and a seal coat but have been disappointed with the results. I am wondering if there is a better alternative to zinc chromate for corrosion protection? My primary concern is corrosion, my secondary is long term appearance. I also need to hold a tolerance because this shaft is fixed inside a bearing.

Pictures are close ups of the part that were on the same trailer over the past winter (two parts per trailer). I'm not sure why the first red rusted more than the second.

55998-1 55998-2

55998-3 55998-4

I have talked to several different plating companies, but I'm not convinced they are trying to sell me the best plating for my application rather than just "their" plating. This material is 1018 round shaft with an A36 mild steel fabricated sprocket.

I would appreciate any information you can provide.


Kevin Heider
semi trailers - Humboldt, Iowa

October 26, 2010

I would at least try 0.001" of electroless nickel. This will normally come out with a bright finish. If you need matte, grit blast the parts just before plating.
It costs quite a bit more than zinc, but it lasts a lot longer when in contact with wet salt.

James Watts
- Navarre, Florida

October 28, 2010

Hot dip zinc galvanizing will last much longer, primarily because it is much thicker. It will turn gray after six months or a year, about the same as your electroplated zinc.

To see what hot dip looks like and how long it lasts, look at Armco barriers along the highway.

If the extra thickness of hot dip doesn't cause dimensional problems, you will probably find it not too expensive and much more durable.

jeffrey holmes
Jeffrey Holmes, CEF
Spartanburg, South Carolina

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