Dull Surface

The dull grey colour can be attributed to two main things-

1. It is the colour of the zinc-iron alloy.  This is often covered by a layer of pure zinc that has frozen on the surface when the item has been withdrawn from the bath (similar to having a layer of water left on your skin when you get out of the pool).  When there are higher silicon levels, thicker steels or items with inadequate venting, the layer of ‘shiny’ zinc gets used up in the zinc-iron alloy and the surface becomes a dull grey.  There is no problem with this and the coating is usually thicker and harder.

2. Old galvanizing often ‘dulls’ off.  This is due to the zinc reacting with the carbon dioxide in the atmosphere to form a ‘patina’ (thin layer) of zinc carbonate.  This zinc carbonate is a dull grey colour.  The patina is the reason that most galvanizing ‘fades’ to a more uniform dull grey colour.  The patina provides another layer of protection for the steel and enhances the life of the item.

grey, dull, gray, matt,

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