"Corrosion resistance of 17-4 PH stainless steel"

Question:

"I am an engineer for a small aerospace manufacturing company and we are working on a part made from 17-4 PH stainless steel. The heat treat condition is H1025. This material was chosen because of corrosion resistance and it's good fatigue life. The part is a hinge on the landing gear system of an aircraft, so it will be exposed to the atmoshere in coastal areas and may repeatedly get wet from water on a runway. We are trying to figure out if the corrosion resistance of this material is good enough to put it in service as bare metal or if it needs a coating or chemical treatment. Also, if 17-4 in this heat treat condition has corrosion resistance good enough to use as bare metal, how smooth should the surface be. We are currently planning on grit blasting with aluminum oxide at 240 grit to remove the scale from heat treatment. Will this reduce the corrosion resistance? If you think a coating or chemical treatment is necessary , which do you recommend? Any coating applied will have to either be clear or thin enough to inspect welds made prior to heat treatment."

Answer:

Given the depth of your questions, it is not practical to respond to your post in this forum. Your situation is one for a study, not casual response in a discussion group. For instance, you asked weather 17-4 PH will have sufficient corrosion resistance for an aircraft landing gear hinge without providing information on how much corrosion can be tolerated, weather pitting is critical or any design related information. Surface finish can affect corrosion resistance; however, again it would not be prudent to quantify its effect in your specific case based on the criticalness of the hinge to the safety of the aircraft.

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