Measuring the atmospheric corrosion of Q235B and T91 steels using gray value, wavelet analysis and fuzzy Kolmogorov-Sinai entropy

Purpose This paper aims to quantify atmospheric corrosion by image analyses. The corrosion extent, form and distribution of corrosion product on Q235B and T91 steels exposed to a Zhoushan marine atmosphere over one year are characterized by image analysis. Design/methodology/approach Image analysis of corrosion images were achieved using the gray value, wavelet analysis and fuzzy Kolmogorov-Sinai (K-S) entropy. Findings As corrosion becomes extensive, the gray value of corrosion images decreases, and the energy value of nine subimages after wavelength decomposition decreases. Fuzzy K-S entropy increases as localized corrosion propagates but decreases as uniform corrosion spreads. Originality/value The methods proposed in this work open a new way for fast corrosion evaluation of metallic materials exposed to atmospheric conditions.