stub and thread protection
how to prevent coating forming on your steelwork
managing the integrity of your product
When galvanising a steel article, it may be a requirement to prevent a coating from forming in certain areas which perform special functions.
This includes the following:
- Threads or axle stubs
- Drilled holes
- Surfaces which will be subject to welding after galvanising
There are several different methods that may be used to prevent a coating from forming on the steelwork. We offer friction taping of items to avoid zinc coating.
We protect the items by tightly wrapping a high temperature friction tape around relevant areas to prevent the ingress of molten zinc. This tape withstands the caustic cleaning and pickling processes, although charring or a carbon residue might be produced with some products. This can easily be removed with brushing.
preparation of threads
When assemblies to be galvanised incorporate threaded components, the tolerance normally allowed on internal threads must be increased to provide for the thickness of the galvanised coating on external threads. Standard practice is to tap nuts oversize after galvanising. The galvanised coating on the stud provides corrosion protection for the internal thread.
The standard size for oversize tapping/ thread creation is 0.2mm.