SES partnered with MTI to conduct a study to understand the impact of different surface treatments of metal surfaces on the adhesion of a composite pipe repair system using coupon level lap shear and peel specimens. The metals used in the study were carbon steel, stainless steel and Alloy C276 and the surface treatments included NACE Rust grade C, grit blast to near white metal finish, wire brushed and solvent wiped. Resins in the test matrix included typical vinyl ester resins based on Bisphenol A and novolac epoxy backbone, both were tested with and without a primer. The test results showed that increasing the surface area of the metal using grit blasting offers the most consistent technique of enhancing adhesion of the composite wraps on the metal surfaces. Adhesion was largely a physical phenomenon where the increased surface area provided by grit blast allowed for physical tethering of the resin on the treated surface. The impact of solvent wipes was indistinguishable from the corroded baseline surface, and the impact of wire brushing was also minimal. Adhesion failure of the primer or unprimed resin on the metal surfaces was the principal mode of failure. SES recommends an additional study to quantify the performance of newer resins that are specially formulated for enhanced metal adhesion.
Date Recorded: January 31, 2024
Instructor: Andy Palsule & Colton Sheets, Stress Engineering