Galvanizing is what you see on a metal bucket, you can see the zinc crystals, and the surface is not suitable for wear. Zinc acts as a sacrificial anode, protecting the base metal. It is possible to get much nicer finishes with proper processing, many panels in cars are galvanized.
Phosphatizing yields a more attractive finish, which may be suitable as a wear surface. Parkerizing and gun blueing are two examples of phosphatizing. It is generallly considered a surface conversion coating in that the chemical process permeates into the surface. Most of the modern processes include other components such as manganese and/or nickel. This type of finish usually relies on oil on the surface to enhance corrosion resistance.
Further to ghillis response
Galvanising is a process of applying zinc to a metal usually steel.
There are two commonly recognised processes-
Hot dip galvanising where the part is immersed in a molten bath of zinc and the zinc allowed to alloy with the steel substrate forming a metallurgical bond.
Electro-galvanising where the zinc is applied to the steel by passing the steel through an electroplating bath containing solutions of an appropriate zinc salt usually in a continuous process. in this process there is no alloy layer between substrate and coating.
Phosphate coatings are applied by immersion in a proprietary solution of aqueous phosphoric acid and additives. A chemical reaction occurs between the substrate and the solution forming zinc or zinc iron phosphate crystals to form on the surface of the substrate. Where galvanised parts can be used as is it is usual to apply oil or an organic layer to enhance the corrosion resistance of phoshated components.
