Iron castings of any type and any chemical composition can be hot dip galvanized. The most commonly galvanized iron is Spheroidal graphite cast iron. Galvanizing of this provides a coating similar in thickness and structure to that produced on normal carbon steel. Other cast irons i.e. Blackheart Malleable, Perlitic malleable and Whiteheart malleable iron are hot dip galvanized successfully. While the pre-treatment process prior to the galvanizing of steel, entails degreasing and pickling in acid, castings also require to be abrasive blast cleaned prior to a brief rinse in acid. This is due to the presence of foundry sand on the surface of castings which normal pickling acids cannot remove. Most castings are abrasive blast cleaned by the foundry after manufacture but the degree of surface cleaning is invariably insufficient if subsequent hot dip galvanizing is required.

Galvanizers who specialise in the processing of castings, provide an in-house facility for abrasive cleaning these products..

In the past, hydrofluoric acid was used to remove foundry sand from casting surfaces. This practice has been discontinued because of the severe health hazards associated with its use.

The galvanizing of castings has no detrimental affect on the mechanical properties of the material. Temper embrittlement has, however, been encountered in nodular cast irons reheated within a temperature range of 375ºC to 575ºC. The presence of elements such as antimony, tin, phosphorus and arsenic may also produce temper embrittlement during galvanizing. Phosphorus levels should be kept below 0.02% to 0.04%. Molybdenum (0.10%) has a very marked effect in preventing this brittleness and thus it has become a standard addition to cast irons and even some steels where embrittlement must be avoided. Water quenching from a temperature of 650ºC prior to galvanizing will also avoid embrittlement in a susceptible cast iron.