Influence of cathodic protection on the lifetime extension of painted steel structures

• Published in: Metals and materials international Vol. 12; no. 3; pp. 255 - 261
• Main Authors: Yoo, Y. R., Cho, H. H., Take, S., Kim, J. G., Kim, Y. S.
• Format: Journal Article
• Language: English
• Published: Seoul Springer Nature B.V 01.06.2006; 대한금속·재료학회
• Subjects: Anode effect; Anodic protection; Cathodic protection; Coating; Corrosion prevention; Corrosion tests; Painted; Paints; Protective coatings; 재료공학
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/BF03027540

For corrosion to occur on a coated metal surface, an electrochemical double layer must be established. Hence, the adhesion between the substrate and the coating must be weakened to enable a separate thin layer of water to be formed at the interface from water that has permeated the coating. To prevent the failure of a painted coating, we applied a cathodic protection method. This method has been controversial for a few years because cathodic protection can induce cathodic delamination of the entire surface, especially near the anode, and also because it is not effective on a not-wetted surface from the anode. We therefore evaluated the efficiency of cathodic protection for 700 days in an atmospheric environment and performed surface observation, AC impedance measurements and corrosion tests. In the case of a noncathodic protected painted steel specimen, blisters formed after 100 days and grew in number for the remainder of the test. However, cathodic protection of the painted steel increased the coating resistance and extended the lifetime of the coating. According to our calculation with the BEASY program, the thickness of the water film under a rain condition barely influenced the protection potential. The high voltage of the cathodic protection and the subsequent cathodic delamination caused the paint to peel off near the anode. Hence, the protection voltage should be controlled in accordance with changes to the environmental condition.