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).

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11 comments

    we look for high temp. crews and nuts, if you have I send the measures and quality and quantity,
    thanks, best regards: István Vereckey

    Can an A193 Gr B7 Stud with Zinc plating be used in application involving 650°F temperature ?
    Its goes on spools that operate at this temperature.
    If not, can you recommend the type of plating to be use on the A193 B7 stud for this high temperature application.

    @Mathew- Appendix 2 from ASTM A194 recommends against using zinc coated fasteners above half of the melting point of the zinc. Zinc melts at 780F, so it is not recommended to use zinc coated bolts above 390F. As for other, higher temp platings, we are uncertain. We are aware of specialty coatings like teflon, or xylan, but we don’t have enough experience with those coatings to know how suitable they are for higher temperatures.

    I understand that the typical paper staple is made of zinc-plated steel. If that is not correct, please let me know the correct components. What I specifically need to know is what reaction a staple might have if exposed to temperatures 350 F or higher. Can they turn black, or dark?

    I will greatly appreciate your feedback.

    Thank you,

    Maria Byrne

    Thank you for your prompt response. I just found that specifically, they are made of steel alloy which consists of Iron and Carbon (plus small amounts of alloying elements). If a staple of that composition were to be cooked in with food in high heat in a skillet or wok, what would be the physical effect?

    Thank you.

    We need suitable bolts to fit up pipes of main engine exhaust line. This exhaust line pipe dia 500A and that pipe line consist with silencer. Pls advice us to select suitable bolts to fit up pipe line from main engine exhaust outlet to silencer inlet and silencer out let to end of exhaust outlet.

    @TCV Desaa – I am sorry, but without any engineers on staff, we are unable to recommend bolts for this application.

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