Galvanising is the process of applying a protective zinc coating to steel or iron, to prevent rusting. Typical applications where galvanising has been used at Stratford Metal Fabrications are external structural components. The protection provided by galvanising is insufficient for products that will be constantly exposed to corrosive materials such as salt water. For these applications, we suggest a stainless steel solution.
Technical bit: The most common method is hot-dip galvanization, in which parts are submerged in a bath of molten zinc. Galvanizing protects in two ways:
- it forms a coating of corrosion-resistant zinc which prevents corrosive substances from reaching the more delicate part of the metal
- the zinc serves as a sacrificial anode so that even if the coating is scratched, the exposed steel will still be protected by the remaining zinc
The hot-dip process does generally not reduce strength on a measurable scale, with the exception of high-strength steels (>1100 MPa) where hydrogen embrittlement can become a problem. The size of crystallites in galvanized coatings is a visible and aesthetic feature, known as “spangle”. By varying the number of particles added for heterogeneous nucleation and the rate of cooling in a hot-dip process, the spangle can be adjusted from an apparently uniform surface (crystallites too small to see with the naked eye) to grains several centimetres wide. Visible crystallites are rare in other engineering materials.