Study On Cathodic Delamination Behavior Under Damaged Coatings By Means Of Array Electrode Techniques

As the most economical, simple, and widely-used mean for corrosion protection, organic coatings have received great popularity among the corrosion protection workers. In real life, the flawless coatings are difficult to accomplish because of the formation of barely visible micro cracks or holes, due to solvent volatilization, polymer chain crosslinking and other reasons during the film formation process. Besides, coating failures can also be inevitably caused during the transportation of coated equipment. So it is more practically significant to study on the deterioration process of coating damages. The research of damaged coating failure behavior contributes to the development of long life of coating technology which can be resistant to damages.In this thesis, it studies on cathodic delamination behaviour and mechanism under damaged coatings by means of Array electrode. Firstly, a comparative analysis of the potential distribution, current distribution and impedance distribution correlation array electrode coating damages system, confirmed by a closer correlation of current distribution and resistance distribution, confirmed more than 1μA·cm-2 current density peak and less than 106Ω ·cm2 impedance of coating failure region is logarithmic linear correlation. On this basis, establishes the evaluation of damaged cathode stripping migration velocity of cathode coating is lower than the area of parameter Scstrip, and the use of this parameter to evaluate the damaged coating cathodic delamination behaviour, and further expand the cathodic migration velocity, breakage impact area on cathode stripping process, study impetus and migration behavior of migration characteristics of cathodic disbonding area to the coating intact area, obtained the following research results of damaged coating, the cathodic delamination behaviour to get deep understanding.(1) Confirmed that the damaged coating failure process in current distribution and impedance distribution has a closer correlation. According to this correlation it is proposed for the first time evaluation of damaged coating cathodic delamination behaviour of the cathode stripping ratio parameters in the study area, and made a successful application of this parameter evaluation of damaged peeling behavior of cathode coating area.(2) Confirmed that the damage zone anode area to keep the tendency in the damaged area of rust layer of cathode area; tendency to adjacent coating cathode stripping area on migration, its function mechanism and demonstrate;(3) Found damaged zones more small cathode stripping zone migration velocity increasing, the greater the damaged area cathode migration speed decreases the coating damages to Cathodic Delamination behaviour characteristics, and this seems to violate conventional behavior demonstrated electrochemical corrosion mechanism.(4) Confirmed the existence of 4 electrode system damaged coating process, coating process, coating intact area electrode porosity osmotic region electrode process, damage zone and fracture zone near the anode process of cathode coating zone stripping process. And the establishment of relevant equivalent circuit model;(5) Confirmed the damaged coating cathode zone of high pH value, more positive potential and oxygen reduction reaction product of OH- enrichment was likely to cause the coating peeling.(6) Confirmed the damaged coating cathode stripping process tends to regional migration adhesion is weak expansion.