Corrosion of stainless steels 3

[slv122]

i need to know, what is the most corrosive resistent stainless steel. we are debating between 316 and 304. 316 is subject to more pitting and crevice corrosion. also what is the best method of testing them. we need to determine about how long they will go without corroding.

 

[TVP]

You need to provide additional information before you will obtain proper respsonses. What is the environment? Temperature? Presence of chemicals, gases, etc.? What type of components are you investigating? Are they highly stressed, to where stress corrosion cracking is a concern? Is abrasion or wear a concern?

In general, Type 316 is considerably more corrosion resistant that Type 304. This is due to the addition of molybdenum, which promotes exceptional passivity, even in the presence of chlorine. It should be MORE resistant to pitting and crevice corrosion than Type 304.

There are many test methods for evaluating the corrosion behavior of metals, including stainless steels. If you provide additional details, we can recommend an appropriate test method based on the environmental conditions, etc. Also, I would recommend that you post this question to the CORROSION ENGINEERING forum located under the MATERIALS ENGINEERS section. There may be people that subscribe to that forum who do not subscribe to this one. One expert (mcguire is his handle) that regularly contributes to that forum has a great deal of experience in stainless steel, corrosion, etc.

 

[mcguire]

TVP is right. It's hard to find questions except by the most correctly aligned forum. There are several FAQ's in the corrosion forum that should help you and another website,

http://www.stainlesscenter.com,

which has a lot of data.

 

[quark]

SLV1221!

SS316L is more resistant to corrossion. (L stands for low carbon content, lessthan 0.3%) This prevents carbide precipitation at grain boundaries thus reducing crevices and stress cracking.

But as TVP said what is your environment? Any bloody steel near a DM Water Plant (demineralised) area will corrode because of acid fumes. Further SS cannot with stand anhydrous caustic. (there is a disease called caustic embrittlement for stainless steels)

Regards,

Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.

 

[stanier]

Look to

http://www.nidi.org

for hundreds of technical papaers on the use of Stainless Steel.

 

[slv122]

i need to know, what is the most corrosive resistent stainless steel. we are debating between 316 and 304. 316 is subject to more pitting and crevice corrosion. also what is the best method of testing them. we need to determine about how long they will go without corroding.
as to what we plan to use this for, it is used to hold gears in a water motor that run a lawn sprinkler. it will be in a water motor that will be submerged in water (all types) for lenghts of time. i read that the sea water (fog) test is the best method. i also need to know if this test is best and how long should you run this test for.

 

[mcguire]

316 is distinctly better than 304. Use 316L only if welding. Otherwise it is no better than palin 316. #16 is fully adequate to resist any water one would put on a lawn.
It would be only marginally adequate for seawater.
Specify 0.002% maximum sulfur. Do not use abrasively-produced surface finishes unless you subsequently passivate.
Any test you do that is not a test of the actual service is no better than an expert opinion because it is an extrapolation from test conditions to actual conditions. It won't prove anything. These alloys are very well known and their performance under known conditions is available.