抄録
Zn-Al composite baked coating is used practically applied to automobile small component because it has good corrosion protection even if thin coating. However, automobile is used all over the world, so this is exposed to a wide range of corrosion condition. This study focused on the influence of sulphate ion and chloride ion. The test of corrosion protection of Zn-Al composite baked coating was done using the solution which contains those ions. Simple immersion test and wet-dry cycle immersion test were experimented for 4 weeks. The evaluation of coating was done about corrosion potential monitoring, electrochemical impedance spectroscopy (EIS) and X-ray Diffraction (XRD). The results mean that a clear difference in both solutions could not be confirmed in the immersion test. In the wet-dry cycle test, the change of time of potential showed the same tendency, but impedance date appeared as the clear difference after four weeks. Moreover, as a result of XRD revealed that corrosion product layer(simonkolleite) is formed in an aqueous solution of sodium chloride .This corrosion product because a diffusion barrier and influence strongly in the preservation of the film from the result of the EIS.
