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Type 416 stainless steel shafts are rusting

We are facing a very serious problem. We are using Carpenter Steels Grade T 416 Stainless Steel at our India Plant. We have finished screw machining of 3" long shafts and have done centerless grinding on them. After that we did the following for cleaning them :
1. Cleaned in Mild Soap Solution
2. Ultrasonic Cleaned in solution of soap , IPA (Isopropyl Alcohol), and Water
3. Water Rinsed
4. Water Rinsed
5. IPA Dip again
6. Hot Air Drying

After some time we found rust spotting on the parts. Now did we go anywhere wrong and did we not follow the correct procedure. What kind of passivation should we do here, and what is the concentration of the passivating solution to be used. The material here is SS 416 Grade T (tempered).

Sanjeev Malhotra


Dear Sir:

We do not see any reference to the method of passivation in your letter. The procedure you described will remove moisture temporarily, but will not provide any corrosion resistance.

There are a number of methods commonly used for passivation. The latest specification we have seen is ASTM A967 [link by ed. to spec at TechStreet] .

For 400-series alloys, we would recommend electropolishing as the preferred method. In India, we would suggest that you contact Mr. Kumar Shah of Progressive Chemical Co., 28-29 Agrawal Industrial Estate, Bombay, India, 400068. Mr. Shah produces electropolishing chemicals under license and should be able to prescribe a local product for your application.

Good luck.

Ed Bayha
Metal Coating Process Corporation - Charlotte, North Carolina


YOU CAN USE NATURAL LEMON OR NITRIC ACID OR citric acid [linked by editor to product info at Amazon] FOR REMOVAL OF RUST


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