What is the maximum service temperature limitation for hot-dip galvanized fasteners?
The answer to this question can be found in the appendix of the ASTM A194 specification, which deals with nuts for high temperature or high pressure service. Specifically, section X2.1 – Coatings and Application Limits. In this section it states that coated fasteners should not be used at temperatures above one half of the coating’s melting point. The melting point of elemental zinc is approximately 780° F (415° C). Therefore, zinc coated fasteners, whether zinc plated or hot-dip galvanized, should not be used in applications where they will be exposed to temperatures exceeding 390° F (210° C).