"CORROSION OF ASTM A182 (Grade F6NM) & ASTM A487 (Grade CA6NM-Class B)"

Question:

"If the above metals have been exposed to metallic surface contamination, will the metals continue to corrode indefinitely or until the surface contaminants have been removed? One other question, you note within your web site three methods of cleaning stainless steel (e.g., nitric acid paste, blasting with wallnut shells or glass beads, & polishing) how would you rate each method's effectiveness for removing metallic contamination?"

Answer:

I assume in responding to your post that the matallic contaminent you are referring to is carbon or low alloy steel. If, so then normally I would expect the corrosion to cease once the corroding material is consumed. An occurrance where this might not hold true, is if, during the corrosion process, an autocatalytic cell was set up that provided its own driving force. Of the three cleaning methods you mentioned, hot nitric acid should be the most effective for removing embedded iron/steel contamination. You may also want to review ASTM A-380, Cleaning Stainless Steel... See ASTM's bookstore and search for A-380 at http://www.astm.org.

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