What is the cause of extreme premature corrosion on submerged equipment after 90 days in water south of Brazil?

Equipment was coated with marine grade paint. Bolts and nuts had severe corrosion at thread interface and at contact points with flange. Was also widespread over rest of equipment. Photos available.

Hi Ed: This sounds like a case of galvanic corrosion, an electrochemical type of corrosion, and is the result of the nuts and bolts being of a different metal to that of the main equipment. This type of corrosion is particularly rapid in sea water because movement of ions is involved in the process.
See:

http://en.wikipedia.org/wiki/Galvanic_corrosion

Hope this solves the problem. dr p

This entry was posted on Sunday, June 27th, 2010 at 9:59 am and is filed under corrosion. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

2 Responses to “What is the cause of extreme premature corrosion on submerged equipment after 90 days in water south of Brazil?”

swah on June 27th, 2010 at 3:34 pm

Was it missing a sacrificial anode? A lot of times with iron components used in water, they will have a sacrificial anode made of zinc. This will corrode instead of the iron, and can be replaced every so often.
References :
Roland P on June 27th, 2010 at 4:14 pm

Hi Ed: This sounds like a case of galvanic corrosion, an electrochemical type of corrosion, and is the result of the nuts and bolts being of a different metal to that of the main equipment. This type of corrosion is particularly rapid in sea water because movement of ions is involved in the process.
See:
http://en.wikipedia.org/wiki/Galvanic_corrosion
Hope this solves the problem. dr p
References :

Rust