Simple Measurement of Carbon Film on Phosphorus Deoxidized Copper Tubes by Preparation of a Potential Difference Calibration Curve

Abstract

The copper tubes of heat exchangers for various types of equipment used in air conditioning and sanitary equipment have been reported to show type I pitting corrosion due to the synergistic effects of carbon film and water quality. To quantify the carbon film, the inner surfaces of the tubes after degreasing with acetone are dissolved with a mixture of nitric acid and hydrochloric acid to allow collection and analysis of the attached carbon. However, there are concerns about the difficulty and danger of this procedure. Therefore, a simple and versatile method for quantifying carbon film is required. We prepared a potential difference calibration curve for corrosion potential measurement as a simple means of quantifying carbon film. The results of the present study showed that the carbon film can be measured by preparation of a potential difference calibration curve for the potential difference ΔE 30 s after immersion in 0.5 M KCl test solution at pH 6. It was also confirmed that the calibration curve was useful for actual tubes.