For the Steel Fabricator and Construction Trades Hot Dip Galvanizing is the standard zinc coating to protect against rust. One alternative, when a finer surface finish is required is Electroplating.
Hot Dip Galvanizing is durable and inexpensive when compared to the various other methods available. It does, however, leave a rough, uneven surface with varying visual effects. The surface variations are partly due to the system used to apply the zinc, which is an “un-controlled application” of zinc in its liquid form.
Fig. 1
Shown is Hot Dip Galvanized Slotted Steel Shim. Note the inconsistent
surface.
Electroplating, on the other hand, will produce a very even, uniform and more reflective surface, similar to a gloss finish. This “controlled application” is the result of the zinc being transferred to the workpiece using an anode / cathode system with particles as small as 0.0002”. The thickness of a finished electroplate coating can be as thin as 0.0005”.
Fig. 2
The electroplated shim shows
the consistent and reflective finish.
Due to the thinness of the coating, electroplating will not offer the longevity of Hot Dip Galvanizing. Therefore, it is usually not specified in locations with marine atmosphere, heavy vehicular omissions or constant exposure to the elements.
Fig. 3
The electroplated threads are perfectly clear and the coating thickness is perfectly consistent. In this case Hot Dip Galvanizing would add inconsistency and thickness to the coating, which requires extra tolerance on the nut fit.
Where electroplating does become desirable is when a more visually appealing coating will enhance the finished product, or greater accuracy is required. Fig. 3 shows the consistent finish in the threads on an Anchor Bolt and Threaded Embed Stud. This allows for an exact nut fit with no unnecessary play or clogging in the threads.