Galvanisation involves coating steel with zinc to protect it against corrosion. Zinc corrodes at a much slower rate than steel and this coating will rust first, protecting the steel and prolonging the life of the chain or any other galvanised part. Hot-dip galvanisation consists of quenching the chain in molten zinc at around 450°C. A chemical reaction then occurs that binds the zinc to the steel and creates a surface alloy that is corrosion resistant. The final result will depend on the quality of the galvanisation process, in terms of the amount of zinc applied and the level of adherence. Regarding galvanised chains, there’s a little tip to remember: rub the chain against the edge of the delivery drum. If little flakes of zinc fall off easily, that means the galvanisation is of a poor quality.
Almost all chains can be galvanised. A grade 80 HR chain, for example, can also be galvanised but the treatment will weaken it and reduce it to a grade 60 chain.
There are around 50 industrial sites in France that are able to galvanise in this way, accounting for around 700,000 tonnes of steel (2012 figures).