Stainless Steel Corrosion 1

[SAIL3]

It has been brought to my attention recently that lack of oxyen can cause ss to corrode as quickly as bare carbon steel.....I had always assumed that ss was the way to go in a potentially corrosive atmosphere...this issue came up with a coleague who is anchoring a system underground(soil) and was considering using ss hardware.....has anyone encountered this issue?...thanks

 

[Ron]

Stainless steels can be susceptible to anaerobic corrosion and microbiologically induced corrosion. Generally select an alloy that is resistant to sulphate (and resulting sulphide) exposure.

 

[XR250]

I have found that 410 SS fasteners will rust faster than carbon steel.

 

[JedClampett]

There's a thread somewhere on this site (I can't find it right now) dedicated to corrosion. You might get more replies there.

 

[cvg]

stinless steel forum

http://www.eng-tips.com/threadminder.cfm?pid=723

 

[EdStainless]

There is a long term study being done by the government, maybe DOD.
They buried metal samples in trenches.
The dug one up recently after about 40 years.
Corrosion in soils can be very tricky. organic content, salt content, microbes, water, all play a roll in how corrosive the environment is.

In general low alloy SS grades, 410, 420, 304, 316, 201; are not suitable for unprotected burial in soils.

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Plymouth Tube

 

[cvg]

but there is oxygen in the soil, the experiment did not control the environment for oxygen, so really does not address the original post. the post also does not address the other environmental factors in the soil as Ron indicated, pH and sulfates (think weak solution of sulfuric acid) can be just as damaging as normal oxidation. Typical practice is to take soil / ground water samples, test for sulfates, pH etc. and then get an opinion from a geotechnical or even better from a corrosion engineer.

be careful with stainless steel connected to carbon steel, you will have galvanic potential at the connection which can cause the corrosion. you need to avoid connecting dissimilar metals.

 

[SAIL3]

thanks for the response and info......in the past, my only consideration for using ss was the cost...now this definitely muddies the waters.....I have used ss anchor bolts without any worry about anaerobic corrosion up to now...what about areas where one has a flat washer in contact with a nut/head where there is possibly an anaerobic condition.....I understand now that oxygen creates a surface film of corrosion on ss which protects against any further corrosion....