The metalized coating may be left bare or as-sprayed; it may be sealed with a low viscosity penetrating sealer or, in a limited number of circumstances, the sealed-sprayed metal coating may be topcoated with paint.
As-sprayed zinc is a standalone coating that can be supplemented and improved by the application of a sealer. Sealing the sprayed metal lengthens the coating’s service life for a very modest cost.50 The addition of paint over the sealed sprayed-metal does not necessarily improve the coating’s service life in the same way that sealing does.
We rely on the British Standard and other sources to explain the application, function, and benefits of sealing and topcoating.
As previously explained, the bare metallic coating is both a barrier and a galvanic coating. Zinc, and to a lesser degree aluminum, protects steel by corroding in preference to the underlying steel.
When the bare galvanic coating is consumed, maintenance will be to blast clean the steel to the required cleanliness and profile, followed by the reapplication of the sprayed-metal
The low viscosity penetrating sealer as defined below penetrates and closes-off the sprayed-metal coating’s porosity or as ISO 2063 reads,
The purpose of sealing is to reduce inherent porosity of the sprayed coating.51 Moreover, sealing preserves the sprayed-metal and prevents its galvanic consumption.