Steel stud corrosion stress problem?
Steel stud corrosion stress problem?
(OP)
I have an application where I want to use a carbon steel (SAE J429) grade 8 stud to hold a piece of equipment to its foundation. It is a 1.125" stud that will be torqued to 650-700 ft-lbs. I'm hearing there is some concern about some kind of stress corrosion cracking or hydrogen embrittlement in highly stressed carbon steel fasteners in a possibly wetted environment. Can anyone explain what the issue may be, or point me to somewhere I can learn about this potential problem?
Thanks in advance for any assistance offered.
Jim
Thanks in advance for any assistance offered.
Jim





RE: Steel stud corrosion stress problem?
You can learn a huge amount regarding this issue. First, perform a search on this site using the term "hydrogen embrittlement". Next, you can perform an Internet search (e.g. Google). Other places to look include standards development organizations (ASTM International, SAE International, ISO), materials suppliers (Carpenter, Allegheny Technologies, etc.), and coatings suppliers (Doerken, Magni, etc.).
Regards,
Cory
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RE: Steel stud corrosion stress problem?
RE: Steel stud corrosion stress problem?
RE: Steel stud corrosion stress problem?
RE: Steel stud corrosion stress problem?
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Lotsa good stuff on your problem.
"Grade 8 bolts are sensitive to hydrogen, which causes hydrogen embrittlement. You have to be careful, therefore,
about what corrosion protection coating you use in what environment: in certain environments some
coatings will release atomic hydrogen into the fastener."
RE: Steel stud corrosion stress problem?
RE: Steel stud corrosion stress problem?
RE: Steel stud corrosion stress problem?
With that being said, at the low clamp load levels that you will be seeing at that torque level you should not have problems with either SCC or embrittlement cracking. The suseptability of fasteners to those two failures tends to be proportional to the hardness of the parts (UTS) and the applied stress (clamp load). Low lovels of one or the other greatly reduce the potential for failures.
Dick
RE: Steel stud corrosion stress problem?
Also, per the NSTM referenced above by arto, hydrogen embrittlement is only a concern for fasteners with a tensile strength above 150 ksi. SAE J429, Gr. 8 tensile strength is right at 150 ksi, so it sounds like I may be borderline as is, and if being preloaded only to 60% of proof makes it even less susceptible, maybe I have good argument for my stud material?
RE: Steel stud corrosion stress problem?
The minimum tensile strength requirement for Grade 8 bolts according to SAE J429 is 150 ksi, so all of them will be susceptible to hydrogen embrittlement. Even with the coatings that you mentioned, this will not be a conservative design for 50 years of service. Are you sure that the coatings for the rest of the structure also apply to the bolts, or is it possible to use high performance organic coatings such as Magni, Doerken, or Metal Coatings?