Determination of time dependence of coated metal electrical and electrochemical parameters during exposure using principal component analysis

The use of the principal component analysis (PCA) permits the complex and quantitative analysis of the time dependence of electrical and electrochemical parameters of coated metal obtained by fitting impedance data. So far, changes in electrical and electrochemical parameters during exposure were analyzed independently. In this way, some of the information contained in the relationship between changes in parameters over time are lost. In the approach presented, in order to overcome this drawback a correlation analysis using the principal component approach was proposed. The results of this analysis, a 'correlation circle' plot shows a projection of a set of parameters and time onto a two-dimensional plane. The high level of correlation of the given parameter with exposure time means rapid changes in the properties described by this parameter in the system under study, and the low level of correlation indicates small changes and testifies to the durability of the features described by the given parameter. The usefulness of this approach for analysis of time-varying impedance data has been illustrated by example of coating applied on hydrophobic and hydrophilic substrates.