Expert: Alexandre Guimarães Botelho - 1/11/2009

Question
I'm doing a science project and I need to know which metals are most commonly used in construction. I plan to place them in salt water and see which oxidizes the fastest. Thanks for your time. I would really appreciate it if this was answered ASAP, but of course, beggars can't be choosers. Thanks again.

Answer
Dear Naomi,

That will depend on the segment. For oil&gas, we use mostly low and medium carbon steel, and stailess steels of grades 300 and 400.

Since you plan to test in salt water, you may try an excellent example by Pourbaix. Wrap a common 304 stainless steel plate (such steel used for cooking pans) with a rubber band (such as used for money) so as to stretch the band across it. Leave it inside salt water and see what happens to the so called "corrosion proof" steels.

Usually, carbon steels corrode faster on salt water, but that depends on how is corrosion important to you. For pressure vessels, a wall loss is as important as a small bore made by pitting corrosion, since it breaks the vessels containment.

Also, for salt water use with low oxygen, carbon steel with 5% Cr content is used for some applications.


Good luck,

Best regards,

Alexandre Botelho