Hot-Dip Galvanizing vs Zinc Plating

Hot-Dip Galvanizing vs Zinc Plating

by Portland Bolt 94 Comment

Hot-dip galvanizing is a process of applying a protective zinc coating by dipping product in bath of molten zinc. Galvanizing is a favored method of protective coating due to its low cost, ease of application, and long maintenance-free service life. Generally applied at 830 to 870 degrees, the zinc will bond with the steel. It is the most common outdoor protective coating in use. When used on bolts, due to the thickness of the zinc coating, all galvanized nuts must be tapped oversize.

Zinc plating or electroplating is a process where zinc is applied by using a current of electricity. It is a thinner coating than hot-dip galvanizing making it unsuitable for outdoor applications. Its advantages are its brightness and uniform color making it more aesthetically appealing.

The ASTM specification covering hot-dip galvanized fasteners is F2329, while the specification covering zinc plated fasteners is F1941.

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94 comments

JMG

What is advantage and disadvantage of hot dip vs zink plated stud nut bolt?
How can convey for client zink plated in place of hot dip galvanized stud bolt in natural gas service pipe lines

Reply
    Dane McKinnon

    @JMG- Hot dip galvanizing is a far superior coating in terms of longevity and corrosion protection, but it does require overtapped nuts. Zinc plating is a thin, mostly aesthetic coating that is shiny and pretty, but will not protect the fastener as well as the hot dip process. If your client has specified hot dip, we would caution against substituting zinc plated parts.

    Reply
Jhonny Gutierrez

Good morning, in the case of the F436 heavy structural scrapers, only the black finish and the hot-dip galvanized finish are considered, is there any reason that ASTM has not considered the electro-galvanized finish for these products?
This is also seen in the A325 structural bolts and their A563 DH nuts, could you help me with this question?

Reply
    Dane McKinnon

    @Jhonny- ASTM F3125 does not prohibit any coating for A325 bolts, and they also do not and cannot list all possible coatings. You are permitted to electro plate A325 bolts and assorted hardware if you wish.

    Reply
Charlie Perry

Galvanizing prep for hot dip galvanizing of small steel fittings:
Thanks for your very helpful forum. A question: For small fittings to be fastened to a structure with hot dip galvanized Gr 5 bolting, can you advise surface prep for the fittings before we take them to the HD galvanizer? Should we sandblast, or is it sufficient just to grind to chamfer the plate edges and clean any slag, etc.?
Thanks,
Charlie Perry

Reply
    Dane McKinnon

    @Charlie- You will need to discuss the specifics with your galvanizer. Some parts need to be sandblasted, while others can be cleaned with acid. The shape, size and configuration of the part will dictate the best way to proceed.

    Reply
Dean Scrutton

What is typically the cost differential between hot dip galvanise and ENP?

Reply
Vipin

Hi,

Do you know , whats the difference between Yellow Zinc Plating and Galvanization

Reply
    Dane McKinnon

    @Vipin- Electro zinc plating with yellow chromate is a very thin, electro-deposited plating, whereas hot dip galvanizing is a much thicker, dip-spin coating.

    Reply

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