Form and rate of corrosion of corrosion-resistant FRP resins

Abstract

The corrosion behavior and mechanism of matrix resins for FRP in aqueous solutions were investigated, comparing these with the corrosion of metals. Three forms of corrosion were found, namely surface reaction type, corrosion layer forming type and penetration type. In surface reaction type corrosion, which was recognized in the corrosion of epoxy resin cured with phthalic anhydride in alkaline solution, the ester bonds in the resin were attacked by hydrolytic reaction with liquid and then dissolved from its surface uniformly. In the corrosion layer forming type corrosion, observed in the corrosion of unsaturated polyester in alkaline solution, the ester bonds in the main polymer chain were corroded by the same mechanism, but crosslinked polymer chain remained. Then the corrosion residual layer was formed. In penetration type corrosion, a large quantity of environmental liquid was absorbed until an equilibrium state was reached, and then the strength of the specimen decreased quite remarkably. This type of corrosion was observed in the corrosion of orthophthalic type polyester in boiling water and epoxy resin cured with amine in sulfuric acid. As a result of measurements of corrosion depth (which is different from the swelling depth or penetration depth of liquid) with immersion time, it was found that the concept of corrosion rate could be applied even in polymeric material. The corrosion rates were dependent on the chemical structure of resin, the reactivity between resin and environments, and the penetration ability of environments into the resin etc.

Keywords:

• composites
• matrix resin
• corrosion form
• corrosion rate
• aqueous solution