50096

SS304L above seawater environment  

September 25, 2008

We want to construct a SS304L pipeline which is to receive sodium hydroxide solution from a ship to our plant site. Because of the abovesea environment (pipe is about 2 metres above sea level), it is a highly corrosive environment.

1. Can you advice me what is the expected chloride corrosion that the SS304L will be facing?
2. What is the most suitable protection for the SS304L pipe? We are thinking of epoxy coating. Is it suitable?

Thank you.

Chan Ubol

Chan Ubol
chemical industry - Jurong Island, Singapore

Hi Chan,

Yes, you will undoubtedly get corrosion of your stainless pipe particularly around the weldes.

Yes,epoxy sounds OK but ensure that it is in a matrix of fibres, not just painted on.

Have you not considered uPVC for the pipe? Epoxy may be a good choice but what about a frp laminate using a vinylester resin?

Cheers

Freeman Newton - White Rock, B.C. Canada

Dear Chan,

Why don't you use AISI 316L ? This performs much better in marine applications regarding corrosion resistance and the cost remains reasonable.

Anyway, for the finish in marine applications I would use electropolished parts/pipes, both with 316 or 304.
This finish realises a much better corrosion resistance than only passivated parts.

Kind regards,

Marc Quaghebeur.

Marc Quaghebeur
- Brugge, Belgium, Europe

Hi Chan,

I'm with Marc.

Why use an inadequate material and then try to protect it, with on-going maintenance of the protection? Much better to start with a material that is suitable for the service environment. 304 would be a disaster. 316 would be borderline OK given your typical ambient temperatures in Singapore. 2205 would be excellent.

Bill Reynolds    consultant metallurgist Ballarat, Victoria, Australia