Hot-Dip Galvanizing Specifications

Hot-Dip Galvanizing Specifications

by Michael Gordian 26 Comment

ASTM A123 does not cover threaded bolts and fasteners. ASTM A153 and F2329 are the ASTM specifications that cover the requirements for hot-dip zinc coating of fasteners.

ASTM A123

This specification covers the requirements for hot-dip galvanizing on iron and steel products made from rolled pressed and forged shapes, castings, plates, bars, and strips. It does not cover threaded fasteners that are centrifuged or otherwise handled to remove excess zinc.

ASTM A153

This ASTM specification covers zinc coatings applied by the hot-dip process on iron and steel hardware. This specification is intended to be applied to hardware items that are centrifuged or otherwise handled to remove excess zinc. A153 is applicable to steel hardware items of Classes A, B, C, and D.

  • Class A – Castings – Malleable Iron, Steel
  • Class B – Rolled, pressed, and forged articles
  • Class C – Fasteners over 3/8” diameter and washers 3/16” and ¼” thick
  • Class D – Fasteners 3/8” diameter and smaller, rivets, nails and washers under 3/16” thick

Since threaded fasteners are spun at high speeds in a centrifuge to remove excess zinc from the threads, they would fall under the A153 class C specification.

ASTM F2329

The standard specification that covers the requirements for hot-dip zinc coating applied to carbon steel and alloy steel bolts, screws, washers, nuts, and special threaded fasteners applied by the hot-dip coating process. Nails and rivets are not included in F2329. It is intended to be applicable to fasteners that are centrifuged or otherwise handled to remove excess zinc.

ASTM F2329 vs. ASTM A153

A153 covers galvanizing on many products including fasteners, while F2329 is specific to threaded fasteners, nuts and washers. The two specifications have virtually identical coating thickness requirements. Also, A153 and F2329 have different sampling requirements; F2329 requires more samples per lot than A153. Portland Bolt can meet the requirements for both F2329 and A153 Class C. Portland Bolt performs hot dip galvanizing of threaded fasteners within our 137,0000 square foot manufacturing facility. Contact us if you have a need for hot-dip galvanized fasteners or with any technical questions regarding hot-dip galvanizing. One of our experienced sales reps will be happy to answer any of your questions.

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26 comments

Rob

hot dipped zinc galvanized as per ASTM A153

Will galvanizing bolts, that will be used for Sub-Sea hydratightightening using AquaMax jacks
permissible, or would the stretching of the bolt under tension remove the galvanized warranty

Reply
gagan deep

hello,
which method maintain m10spring washer hardness 43hrc -50hrc.
why hrc drop in m10spring washer after hot dip.

Reply
    Dane McKinnon

    @Gagan- Sometimes the heat from the hot dip galvanizing operation can slightly soften small hardened items like this. If you are concerned about the hardness dropping, you could look at alternatives platings that do not require heat, like mechanical galvanizing.

    Reply
Phil

Hello. Which ASTM galvanizing designation would apply for 7-foot long, 2″ diameter anchor rods (F1554, Gr55) being installed in a concrete foundation? Thanks.

Reply
    Dane McKinnon

    @Phil- Mechanical galvanizing is usually for smaller, production type parts, so hot dip galvanizing would be the most appropriate coating for your 2 x 84″ F1554g55 anchor bolt.

    Reply
      Phil

      @Dane- Thanks for response. I agree, hot-dip galvanizing would be the way to go in this situation, I am just curious as to which of the three ASTM types mentioned in the post above would be most appropriate (ASTM A123, A153, or F2329)? I am just not entirely certain whether these anchor rods would be classified as a “steel product” (A123) or “steel hardware” (A153 or F2329). Could you please clarify? Appreciate the input.

      Reply
        Dane McKinnon

        @Phil- The hot dip galvanizing process is more or less the same within all of those standards, the difference is how they are handled. Beams and structural members are defined as steel products and are galvanized per A123. Threaded fasteners are handled differently in order to remove the excess zinc from the threads and would fall under A153 or F2329. A153 and F2329 again are more or less the same, F2329 references back to the processes in A153, but goes into more detail with respect to the specifics of threaded fasteners. A153 touches on threaded fasteners, but is not fastener specific. All the ASTM fastener standards refer to F2329 for hot dip galvanizing, so that would be the most appropriate standard to reference.

        Reply
vinay kumar

ASTM A 153 class C specification is suitable for normal bolts which we are using upto 40 kg/cm2 pressure and for temperature upto 90 degree celcius.

Also in which material we are coating or galavanizing.

Reply
    Dane McKinnon

    @Vinay- ASTM A193 and A320 both say that the maximum service temperature for galvanized bolts should not exceed 390F unless caution is used in regard to the potential for liquid hydrogen embirittlement.

    Reply
afif

Evening.im afif.from malaysia.i got problem in my working site.my company now doing the oil offshore platform.im really confius and always asking what is different between hot dip galvanize and hot dip spun galvanize.i received the threaded rod but certificate mention electro plating not hot dip spun as per client requirement.why all fasterner.nut .washer shall be hot dip spun.why cannot hot dip and why people says shall be enough for electroplating only.please explain.

Reply
    Dane McKinnon

    @Afif – The difference between hot dip galvanizing structural articles and fasteners is the spinning. Spinning removes excess zinc from the fastener so that the nut will mate with the bolt. Electroplating is an entirely different process and is a much thinner coating. It is not a dip spin coating like hot dip galvanizing is. If your requirement is for hot dip galvanizing, electroplating would not be sufficient.

    Reply

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