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.
Is it possible to electroplate / galvanize SS 321 ?
If so, what are the possible thickness can be coated ?
What about their lives ?
Can we heat the coated SS upto 500 deg C ?
@Babu – I don’t believe the galvanizing will adhere to the stainless, so I wouldn’t think it’s possible. However, there may be alternative coatings that could be used, however I don’t have any familiarity with them. Any heating/service life will depend on the coating and you would need to get that information from the coater.
can I-beam, channel, tube steel, angle, etc. be electro-galvanized like sheet metal products can???
@Bill Rush – Sheet metal is plated via a continuous feed process, which is a different process than finished parts are put through. The problem you may run into in trying to electro-plate beam, channel, etc is that they may be too large. You will need to contact an electro-plater and find out their length and size restrictions.
Hi,
What is the difference between the torque values of zinc plated and Hot Dip galvanised Bolts, 8.8 Grade
( DIN 7990 )
@Anoop – If you use the torque equation T=KDP as explained on our torque page, the friction coefficient for zinc plated bolts is 0.22 vs 0.25 for galvanized. If you plug in this value to the equation, you will get torque values for zinc fasteners that are roughly 12% lower than galvanized fasteners to achieve the same tension. This is an estimate only, the actual numbers can vary.
What is the chemicals for brightening in Electro-galvanization?
@Morad – We do not do much with electro-zinc and do not have any technical information about it. You will need to contact someone who does electro plating to obtain this information.
hi,
When used on A-36 plate with threaded holes and thue to the thickness of the zinc coating how much bigger I would have to drill the holes in order to screw the SS 304 bolts?
Typically without galvanizing, If I use a SS 304 3/8″ 16 UNC bolt then I bore the plate with a 21/64″ drill in order to tap(3/8″ 16 UNC) the hole.
Thanks for your help.just in this case the thread on the plate is not galvanized.
@Ferney- The holes would need to be tapped the same regardless of the coating on the plate. If the hole is tapped after galvanizing, nothing additional would need to be done. However, if the hole is tapped prior to galvanizing, then you would need to chase the holes again with the same tap after the coating has been applied, in order to clean out any zinc buildup in the threads.