304 stainless steel 4

[tho]

Anyone knows if 304 stainlless steel will rust in salt water? If so, what is its lifespan?

Thanks in advance

 

[hacksaw]

rust? not in the usual sense, lifespan next to nil in your avg service

 

[Paskenell]

Here is something that might help you

http://www.hghouston.com/ss_sea.html

For the fastener market, our company recommends 304 should not be used in seawater environments.

 

[tho]

Paskenell, what would your company recommends to use in salt water environments? Which type of stainless steel grade?

hacksaw, I don't understand your reply....lifespan next to nothing in my avg service? Can you explain....sorry....

Thanks again for all the reply.

tho

 

[Paskenell]

In the fastener line - "above water level" we recommend a minimum of 316 stainless steel be used.

 

[TVP]

tho,

hacksaw is referring to the corrosion mechanism of Stress Corrosion Cracking when austenitic stainless steels are used in environments that contain Cl ions. Conventional red rusting does not occur, but SCC does. Type 316 is the minimum that should be used, and even this grade is not immune to SCC, especially if the stresses are high, or if the temperature is elevated.

 

[hacksaw]

should have indicated "an" avg service. has to do with stresses, degree of aeration and fluid velocity and no microbial growth, etc.,etc....

chloides and 300 series stainless are generally a poor mix

we all agree on that

 

[tho]

Thank you for all the reply. Really helps.

What is the next grade above 316SS that could be used for SCC condition?

 

[hacksaw]

buy the best grade you can afford;likely won't be 300 series

 

[mcguire]

Tho
304 will corrode in salt water by a pitting mechanism. The degree depends on surface finish, steel impurity levels, etc. The loss of mass is small because the corrosion is very localized, but it can cause perforation, which may be very important, as in vessels, or unimportant, as in rebar.
Pitting will result in red rust in and around the pit.
The next better alloy is 316, then 317, then grades like AL6XN. The cost goes up faster than the corrosion resistance. The ferritic stainless steel, 444, will work about like 317 and resist pitting in ambient sea water without the high nickel surcharge. More often people choose 2205 or 2507, the higher chrome duplex grades. These latter grades, 444, 2205 and 2507 give essentially immunity to SCC.