Studies of oxide-free phosphates film surfaces on magnesium, zinc, and manganese by X-ray photoelectron spectroscopy

This thesis focuses on the most common phosphate coatings used in corrosion prevention. The surface chemistry associated with corrosion, and films used in its prevention, were investigated using X-ray photoelectron spectroscopy with an emphasis on the valence band region. It will be seen that this approach has the ability to probe the specific differences in surface chemistry that play such an important role in corrosion prevention. Systems to be studied include: magnesium, zinc, nickel, and manganese. Different magnesium phosphate compounds were used as models for the identification of various films formed on magnesium. Modifications of the standard bench top method of producing oxide free phosphate films were conducted. Using modifications such as changing the chemical concentration, the changing volume of solution, and changing drying methods could change the chemical composition of these films. This manipulation of concentration and drying methods in the case of magnesium phosphate films resulted in different phosphate films being produced: magnesium hydrogen phosphate, magnesium ortho-phosphate, and magnesium meta-phosphate. Manipulation of volume and concentration of the treatment solution in the case of zinc phosphate films results in: oxide free films, films with zinc hydroxide, and very thin films containing zinc hydroxide and zinc phosphate. Finally, the common electroless nickel treatment of aluminum was studied. This treatment produced a surface with the main components of metal and nickel hydroxide.