All anchor bolt grades except A354 Grade BD can be hot-dip galvanized. There are two issues that come into play when galvanizing high strength anchor bolts that have undergone a heat treating process. The first concern is that the mechanical properties (strength) of the quenched and tempered anchor bolts could potentially be altered by submerging them in a tank of 840 degree molten zinc. Since the temperature of the zinc does not come with 100 degrees of the tempering temperature of the heat-treating process, and bolts are only in the tank for 2 – 4 minutes, theoretically the strength of the bolts will not be affected.
The second issue is hydrogen embrittlement, which can lead to premature failure of the anchor bolts when hydrogen is introduced during the galvanizing process. Only very high strength steels are susceptible to this phenomenon, and for this reason ASTM recommends against galvanizing A354 Grade BD anchor bolts. All other grades of anchor bolts can be hot-dip galvanized with no concern of altering the mechanical properties or subjecting them to the potential for hydrogen embrittlement. For a more in depth discussion of this issue, visit this FAQ on Portland Bolt’s main website.