Metal finishing Q&As since 1989

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External rusting of stainless steel pipes in juice plant

2006

Dear Sir
I undertake turnkey projects of piping for bottling industry.At one of the location I supplied s.s. 304 pipes 16 gauge polished, fittings, valves. After one year I received photographs showing external rust on pipes,valves, fittings.
What could be the reasons I need to explain them please guide me.
Similar material was supplied at other locations but no complaint from them.

ABHIJIT KULKARNI
ENGINEERS - MUMBAI, MAHARASHTRA, India

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Various lots of stainless steel can vary greatly depending on source, etc. 304 stainless steel has shown great variation in recent years.
Was the steel passivated after installation? This is necessary to prevent corrosion.
Of course, there are a lot of other possibilities for the difference, like a different environment at this company, etc.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

2006

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2006

kind attn:Mr,Lee Kremer

dear sir

thanks for your reply.
I attach some photos showing rusted pipes,

ABHIJIT KULKARNI
- MUMBAI, MAHARASHTRA, India

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2006

From the photo it appears certain that you already have some pit corrosion on the surface. This will be very hard to remedy. There are a variety of products which will remove the rust from the surface and passivate the surface, but inside the pits it will still continue to corrode.
The cause could be, among other things:
a) chloride environment.
b) steel that had inclusions or other impurities.
c) lack of passivation after fabrication or assembly.
d) grinding or welding of carbon steel in the area after installation without subsequent passivation.

Contact us if you need help.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois