Hot-dip galvanisingHDG

A corrosion protection system in which hot-dip galvanised steel is overcoated with paint or powder coating. The organic coating protects the zinc and the zinc protects the steel at any damage, so a well designed duplex system generally lasts longer than either coating used alone.

A block of a more electrochemically active metal, commonly a zinc, aluminium or magnesium alloy, electrically connected to a structure so that it corrodes preferentially and protects the structure. Anodes are consumed in service and are inspected and replaced as part of planned maintenance.

A primer containing a high loading of metallic zinc dust in an organic binder, usually epoxy, or an inorganic silicate binder, providing galvanic protection to steel in a similar way to galvanising. It requires a high standard of blast cleaned surface so that the zinc makes electrical contact with the steel.

A group of processes, including flame, arc and plasma spraying, in which metal or ceramic feedstock is melted or softened and propelled as fine particles onto a substrate to build up a coating. Thermally sprayed aluminium and zinc are used for long term corrosion protection of steel, while plasma sprayed ceramics provide wear and thermal barrier coatings.