Study on the Adhesive Strength and the Hydraulic Frictional Resistance of Anticorrosive Paint

摘要

Splitting of paint film seems phenomenologically quite analogous to the crack propagation through the continuous body. The tip of splitting represents the boundary separating the continuous body from the broken. The fracture mechanics, therefore, could be applied for the assessment of adhesion of paints in the same line as of adhesive joints in structures. In this paper, a theory has been developed to estimate the adhesive energy of paints. Isophthalic resin coating was splitted from the substrate by wedging and peeled lengthes were measured as a function of the wedge thickness. Employing the theory, adhesive energy was estimated to be 50-100 J/m2, which is quite resemble to the adhesive energy of epoxy resin to alminum alloy substrates. Additionally, the effect of painting on the reduction of hydraulic frictional resistance has been studied quantitatively using three cylinders with different surface roughness. When the relative surface roughness was decreased from 2.5 x 10-5 to 0.6 X 10-5 by painting and polishing, the frictional resistance was reduced by about 2% under the high Reynolds number condition. More effect of painting is expected for ships because the ship Reynolds number is higher than the present experiment.