While hot dip galvanized coatings provide envelope protection for steel, the zinc in the coating will also protect the steel cathodically if the coating is damaged and the bare steel exposed.
The rate of consumption of the galvanized coating will depend on the size of the cathode (the bare steel) and the size of the anode (the galvanized coating). It is essential that exposure of galvanized coatings to cathodic metals and materials be minimised to prevent accelerated corrosion of the galvanized coating.
The following table lists metals in order of their relative reactivity with each other and when considering coatings and materials for maximim durabality, contact between dissimilar metals should be avoided where electolyte forming moisture is likely to be present.