HDG and dual cert A325/A490 bolts
HDG and dual cert A325/A490 bolts
(OP)
Folks,
We received certification paperwork for high-strength bolts to be used on our project. The fasteners have been dual certified to ASTM A325 and ASTM A490. The fasteners have been hot-dip galvanized. I understand there has been a long standing prohibition on galvanizing ASTM A490 bolts due to concerns of hydrogen embrittlement. We specifically state that ASTM A325 Type 1 bolts get HDG and that ASTM A490 bolts get painted, not HDG. Is there anyone that can discuss whether a dual certified bolt could be at risk for hydrogen embrittlement? Thanks.
We received certification paperwork for high-strength bolts to be used on our project. The fasteners have been dual certified to ASTM A325 and ASTM A490. The fasteners have been hot-dip galvanized. I understand there has been a long standing prohibition on galvanizing ASTM A490 bolts due to concerns of hydrogen embrittlement. We specifically state that ASTM A325 Type 1 bolts get HDG and that ASTM A490 bolts get painted, not HDG. Is there anyone that can discuss whether a dual certified bolt could be at risk for hydrogen embrittlement? Thanks.





RE: HDG and dual cert A325/A490 bolts
RE: HDG and dual cert A325/A490 bolts
A charitable explanation might be that they are actually not HDG, but instead coated in accordance with ASTM F 1136, which is water-based dip or spray Zn/Al coating. Does any of the paperwork actually say HDG, or are they just silver-looking?
But, really, I question the dual certification. What size bolts are these? For bolts up to 1", there is a tiny overlap in the required hardness in the two specs. For bolts over 1", there's no overlap at all, so no way they could even be dual-certified. Have you checked the test results against the spec requirement? (Has your supplier?)
Hg
Eng-Tips policies: FAQ731-376: Eng-Tips.com Forum Policies
RE: HDG and dual cert A325/A490 bolts
RE: HDG and dual cert A325/A490 bolts
I just talked to my fastener distributor buddy and he stated that he has never heard or seen a dual certification of A325 and A490 bolts. He also stated that he has never seen or supplied A490 HDG. He also stated that he does get several requests a month about A325 HDG.
He also stated that the only fasteners he has seen dual certified is the occasional A193 B7 and L7 and even this is rare.
He said to be careful in the purchase of any structural bolting as there is some very questionable material coming from offshore. He said they are currently supplying several thousand A394 tower bolts to replace some that evidently were purchased on the gray market.
RE: HDG and dual cert A325/A490 bolts
In addition, no knowledgeable distributor or manufacturer would supply galvanized A490 and I would strongly recommend questioning anything from this supplier. ASTM covers the dangers of galvanizing A490s extensively (A143, F2329, A490 etc).
Adam
RE: HDG and dual cert A325/A490 bolts
Hg
Eng-Tips policies: FAQ731-376: Eng-Tips.com Forum Policies
RE: HDG and dual cert A325/A490 bolts
A325 Head Marking
A490 Head Marking