I have used thin dense chrome and high phos nickle plating for corrosion resistance. I am told the later being better, at 1.5 mils you can get 1000 hours salt spray astm b117. http://www.electrohio.com/Plating/High_ElectrolessNickel.htm We are trying Geomet and Dacromet coating which is very thin like the chrome but we are unsure how and oil seal will ride on a coating layer. We make speed reducers for the food industry and can not use stainless on our input shafts. We want same corrosion resistance as sstl without the thick build up which means we have to mask certain features. What is as good as high phos nickle for corrsion resistance with out build up, wearability being a secondary concern. Our customers washdown the reducers with diluted acids under high pressure then rinse. I can not find a benchmark comparision of different coatings/platings. Any suggestions?