The Effect of Temperature Gradient for Adhesion Durability of Polyethylene-coated Steel Pipe.

Abstract

The adhesion degradation in the wet environment where a temperature gradient exists from a coating layer side to a steel pipe side was investigated about the polyethylene coated steel pipe which has the epoxy primer layer as the surface treatment. When coating layer side was at high temperature and a steel-materials side was at low temperature, the diffusion in the polyethylene-coating layer of water is promoted, and adhesion degradation became faster. The temperature dependence of time to set the adhesion strength (90 degrees peel strength) of a coating layer to 20Ncm-1 for temperature difference 0, 6, 10 and 15 °C are almost same and each activation energy obtained from temperature dependence was in agreement with it of the diffu-sion in the polyethylene coating of water. The relationship between temperature difference DT and time to set the adhesion strength of a coating layer to 20Ncm-1, t20 was obtained. (t20=B/(A+ D T)+C, A, B, C: const) This can be explained by using the equation of diffusion for water through coating under temperature gradient.