Galvanized A193 B7
Galvanized A193 B7
(OP)
Can A193 B7 bolts be galvanized and have no issues with hydrogen embrittlement?
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RE: Galvanized A193 B7
Under normal use, these bolting materials would not be galvanized. I would not recommend it.
RE: Galvanized A193 B7
A reputable bolt supplier I talked to indicated it would have no problem with hydrogen embrittlement and they do sell them galvanized.
RE: Galvanized A193 B7
RE: Galvanized A193 B7
cal123 - found this about the galvanization:
"If the customer requests plating, we will certify the material as A193 B7 "prior to plating." Because the plating process involves high temperatures, reheating the steel can create "Hydrogen Embrittlement" weak spots in the steel. As a rule, we do not want to quote B7 hot dip galvanized."
RE: Galvanized A193 B7
RE: Galvanized A193 B7
With that said, what you do with these bolting materials is your choice. Considering the risks associated with galvanizing on high strength materials, and the necessity for hydrogen controls, more attention to detail is required.
RE: Galvanized A193 B7
ABS Guide for Building & Classifying Naval Vessels: 3.8 Recognized problems:
… “SAE J429 Grade 8, AISI grade 4340, ASTM A574 alloy steel fasteners, and other high strength fasteners over HRC 34 shall not be zinc coated or they could be susceptible to hydrogen embrittlement. Hydrogen can be introduced during the plating operations or in service via the galvanic interaction with the coating. Traditional four hour baking operations are not sufficient to remove hydrogen absorbed during the plating operation. A minimum of 23 hours is needed to remove the hydrogen from the fastener; four hour bakes have been reported to cause the hydrogen to migrate to the fastener/coating interface and make the fastener more susceptible to brittle fracture. When zinc coated steel fasteners are exposed to temperatures over 149°C (300°F) for long periods of time intermetallic compounds form that can embrittle the fastener.” …
Even if you had them baked out for a longer time, it would be difficult to segregate them out from ones with the standard bake - Dacromet might be the way to go http://www.metal-coatings.com/