Comparison of barrier properties for ZRP with partial replacement of Zn by micaceous iron oxide of different commercial quality by means of electrochemical noise

摘要

The corrosion behaviours of ZRP with low Zn content (40 vol. %) and micaceous iron oxide (MIO) of different commercial quality (Miox SF and MioxMicro 30) has been investigated by means of EN measurements performed in 0.05 M NaCl for 22 days. The motivation for doing this was the fact the barrier properties of tested type of coatings can be sensitive with immersion time to formation of structural defects corresponding to some degree of blistering of coating and delamination of the underlying steel. On the other hand possible effects of the surface modification of zinc particles with immersion time due to calcium ions (calcium borosilicate can be present in some types of MIO) have not yet been investigated. Analysis of EN data in both time and frequency domain permits to evaluate if delamination of the underlying steel (changing with immersion time) can be affected by MIO type fillers when Zn content is not successful in protecting a steel substrate efficiently. Possibility of use of EN data in combination with single frequency (1 kHz) impedance test results for the detection of different increased compatibility between modified zinc surface and polymer binder matrix has also been discussed.