In order to clarify the corrosion mechanism of corrosion protective thermal sprayed coatings from the viewpoint of corrosion potential measurement, immersion tests and electrochemical measurements were carried out by depositing the thermal sprayed powders on iron substrates in aqueous Na
2SO
4 solutions. Consequently, the corrosion mass loss of the iron base material when the powders were deposited, became smaller than that of the iron base material without powder deposition, and the corrosion of iron was completely suppressed in Al-5mass%Mg and Zn-15mass%Al powders. The change of corrosion potential with time could be fractionated into Al holding the same potential as Fe, Zn-15mass%Al or Mg holding a lower potential than Fe, and Al-5mass%Mg keeping a more noble potential than Fe. The corrosion protective function of these sprayed powders has a greater effect as a barrier layer to suppress the diffusion of dissolved oxygen than a galvanic couple with an iron base material.
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