ABSTRACT

Protective coatings are often used with cathodic protection to protect steel structures in buried or submerged services. Cathodic disbondment resistance is always on the top of the coating property list required by end users. Many standard test methods for cathodic disbondment are available to evaluate the resistance to cathodic disbondment. However, there is no universal agreement on which standard to run the test. Test parameters like voltage, electrolyte composition, test temperature, test time, sample configuration etc. vary over a wide range among various test standards. Not all test parameters have been specified in the test standards and frequently, the standard test methods are modified by users. It is difficulty to rank coatings based on the test results obtained from different labs. NACE has formed a Technical Group, TG #470 to develop a new standard to include all test parameters on the cathodic disbondment test. A review paper on ”critical evaluation of international cathodic test methods” was published in 2008 to assess many test parameters. Here we highlight special enhancements: (1) to use the high temperature and environmental friendly reference electrode - Ag/AgCl; (2) to define the test temperature measurement procedure; (3) to check the accuracy of the reference electrode; (4) to develop an inexpensive anode isolation method to eliminate the hypochlorite formation, etc.

INTRODUCTION

The submerged and buried steel structures, such as tanks and pipelines, are normally protected by both protective coatings and cathodic protection. Any protective coating on steels with cathodic protection must be evaluated by the cathodic disbondment (CD) test method to evaluate their CD resistance. There are many CD test standards developed in the world. A critical review of the international standards on CD has been published in 20081. There are many test parameters to be considered in the CD test. These parameters shall be specified in the CD test to compare test results among different test labs. The following test parameters have been discussed in the review paper.

This content is only available via PDF.
You can access this article if you purchase or spend a download.