Using Electrochemical Noise (EN) And Electrochemical Impedance Spectrum(EIS) To Study The Properties Of The Anti-corrosion Coatings

Electrochemical impedance spectroscopy(EIS) and electrochemical noise (EN) are the convenient and efficient testing technology to monitor the corrosion destruction process of the organic coatings.The parameters obtained from EIS can reflect the characterization of the protective properties of the coatings.It is a simple process to calculate noise resistance Rn from EN measure;and the difference of the coating degradation process can be analyzed by using the wavelet analysis from EN data.In the present dissertation,an improved cell was used which can measure the same samples with EIS and EN in turn.The advantage of the improved cell is to make relate compare between the EIS results and EN results more credible.In the present dissertation,the degradation processes of the thin polyurethane coatings(13μm)and the thin epoxy/polyamide coatings(24μm) in the 0.05M NaCl solution were studied by using EIS and EN.One of the EIS parameters,the value of polarization resistance Rt of the metal substrate,was approximately equal to the value of noise resistance Rn,and the change trends of polarization resistance Rt and noise resistance Rn were similar.Spectrum noise resistance R_sn⁰(f→0) and noise resistance Rn had the similar development trend for the degradation process of the coating,but R_sn⁰(f→0) was less than Rn.The values of impedance modulus |Z|_f=0.01 were closed to those of noise resistance Rn.The degradation processes of the thicker epoxy/polyamide coatings(80μm) were researched by using EIS and EN.The values of spectrum noise resistance R_sn⁰(f→0) were closed to those of noise resistance Rn.The values of noise resistance Rn were closed to those of pore resistance Rpo.The values of impedance modulus value |Z|_f=0.01 were different to those of noise resistance Rn.The degradation processes of the thick epoxy/polyamide coatings(150μm) were researched by using EIS and EN.The values of pore resistance Rpo were approximately equal to those of noise resistance Rn,and their change trends were similar.Spectrum noise resistance R_sn⁰(f→0) and noise resistance Rn had the similar development trend in the degradation process of the coating.The values of R_sn⁰(f→0) were closed to those of Rn.The values of impedance modulus value |Z|_f=0.01,were different to those of noise resistance Rn.