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.
During Electro Galvanizing of CS fittings why the coating thickness on the outer surface is more than the inner surface.? Is it not possible to achieve same coating thickness on both outer and inner surfaces?
@Jabin- I am sorry, but we are not experts in electro plating, you will need to contact an electro plater in order to determine why that is.
When using HDGAF 1/2″ threaded rod, is it acceptable to use EG nuts? Is there a dissimilar issue when using different kinds of galvanizing? Thanks, Danny
@Danny- Normally, you don’t want to mix plating types. For many grades of bolt, ASTM specifies that the plating types be the same. In addition, nuts for use with HDG bolts are tapped oversize to accommodate the thickness of the zinc. For electro plated nuts, this is not the case, so you could run into thread fit issues.
Is there a limit to the thickness of zinc layer (hot dipped) on bolts and/or nuts? Is a 85um layer a problem to achieve?
@Mahamuka – 85um=3.4 mils. We should be able to get that thickness on our fasteners as an average thickness, but we could not guarantee that there would not be spots that were thinner than 85um. The minimum allowable thickness per F2329 and A153 is 43um=1.7 mils.
Can electroplating be done after hot dipped galvanizing for shinier surface? Will the galvanizing still hold after the plating top coat?
@Akhilesh – I don’t think electro-zinc will adhere over the top of hot dipped zinc, you might need to contact an electro-plater to see if they have other options that would get you the result you desire.
Hi,
I’ve sent hexagon nut for zinc plating.
The zinc plating covered only the outside surface but not the threaded area.
Why
@Rita – electro-zinc plating should be on all surfaces of the nut, including the threads. Thicker coatings, like hot dip galvanizing require that the threads be overtapped after coating, so those threads are bare.