METHOD OF EVALUATING QUALITY OF COATING FILM THROUGH ELECTROCHEMICAL MEASUREMENT

摘要

PROBLEM TO BE SOLVED: To provide a method of evaluating the quality of coating film through an electrochemical measurement that can be carried out desirably for environment and stably, and is a substantial nondestructive inspection. SOLUTION: This method is used for evaluating the quality of an Ni-P coating film 16 formed on the internal surface of the casing 14 of a manganese steel-made cylinder 12. Firstly, a basic treating liquid 10 is prepared from an ammonium citrate solution of 0.1-10% in concentration. Secondly, a pool is formed of the treating liquid in the cylinder 12 and, at the same time, an electrolytic cell is formed by dipping a reference electrode 26 in the pool of the treating liquid and exposing the internal surface of the cylinder 12 and electrode 6 in the pool. Then the potential difference between the casing 14 and electrode 26 formed in the electrolytic cell is measured. Finally, the quantity of the coating film 16 is evaluated by using the measured potential difference as the index for porosity of the film 16.