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.
I use grade 8.8 threaded rods connecting with metric threaded clevis ends (internal threads).HDG affects the thread tolerance.Would electroplating provide acceptable corrosion protection & thread fit?
@David- Electroplating will offer a minimal amount of corrosion protection. Hot dip galvanizing is a far superior coating, but does affect the thread fit.
Hi
Can we do zinc plating instead of zinc galvanising for solar mounting structures
Can we get 80um coating in zinc plating
@Sandeep- You would need to talk to the project engineer about any plating substitutions, but normally zinc plating is thinner and less corrosion resistant than galvanizing. Zinc plating cannot be applied with 80um thickness, 25um is the thickest we are aware of.
Hello Dean,
Please i am hoping you could help me.
I purchase some stud bolts and nuts for one of my client which is suppose to be Hot dipped galvanized.
Upon receipt the client rejected them saying they are electroplated without running any test what so ever.
Since you do a lot of HDG i thought i ask if you could advice me of any TEST that i could carry out to determine if the bolt and nuts are actually electroplated or hot dipped galvanized.
I await your response.
Many thanks for your help.
Kind Regards,
Timothy Nunu
@Timothy- An accurate test would be to use a coating thickness tester, that can give you the thickness, and you can tell by the thickness which coating it is. Hot dip galvanizing is 2-5 mil (0.002″ to 0.005″)thick, whereas electroplated zinc is less than one mil (0.0001″). Another, but less scientific method would be to try a plain, standard nut on the bolt. If it threads on, then the bolt is electroplated. If not, it is likely galvanized. Hot dip galvanized nuts are tapped oversize to accommodate the thicker coating, so not-tapped oversize nuts should not be able to thread on.
Dear Sir, What is the different between zinc plated bolt and GI bolt, which is suitable for Oil and Gas industry?
@Satheesh- Apologies, we are not familiar with what a GI bolt is, so cannot assist with this.
which is best suitable for earthing/grounding galvanized steel or zinc coated steel
@Suresh- Galvanized steel will be more corrosion resistant and therefore will last longer in that environment.