Galvanized steel is galvanized steel, which means that […]
Galvanized steel is galvanized steel, which means that its surface has been plated with zinc to provide a large amount of corrosion protection.
In galvanized steel, zinc is only on the surface, and if galvanized parts are cut, the "unprotected" steel is exposed underneath. However, one of the neat and useful features of galvanizing is that exposed steel does not really begin to rust until all zinc is oxidized. Zinc acts as a "sacrifice anode", protecting the underlying steel by preferential corrosion. As a result, galvanized steel parts may be scratched, drilled therein, and so on, and still maintain corrosion resistance for a considerable period of time.
Stainless steel is a completely different material category, it is steel mixed with chromium. When exposed to the atmosphere, the chromium on the surface forms a protective layer of chromium oxide, which protects the underlying materials from further oxidation. Since chromium is distributed throughout the steel, you can cut, grind, drill, and other stainless steel materials, and the newly exposed surfaces are protected just like the original parts (this is the exception, but this is another issue).