Letter 20009

Seawater piping corrosion  

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We have experienced a problem with a customers coolant piping on offshore units. The cooling circulates fresh sea-water through a cooler to provide engine, fuel, and air cooling. The stainless steel piping has started to corrode and leak at the welded joints. 304 stainless was used for material in the piping and elbows. Is this a form of Galvanic corrosion?

R. Reder
- Calgary, Alberta, Canada

Hi !

You are not the first nor will you ever be anywhere like the last to have problems with stainless in salt water. It keeps and KEEPS coming up.

And you used a mere 304 series, tut, tut. Even 316 has problems. Go the archives and see, I think, # 8544, 7117, 16942 and recently "6a" # 19760

Why in the HECK don't knowledgeable (????) engineers use the right damn plastics to avoid marine corrosion!

Freeman Newton
- White Rock, B.C. Canada quasi retired after 40 years in the thermoplastic fabricating business for chemical plants.

It sounds like it might be a welding problem. If you don't weld SS properly, you get carbide precipitation around the welds. You've then got some prime spots for corrosion. I was saw a customer's process tank almost literally fall apart because of bad welding. I'm no welding expert, but I have heard that 304 is not the greatest for welding. People usually recommend 316L.

Christian M. Restifo
- Pittsburgh, PA