Polymer Linings For Restoration & Corrosion Protection Of Steel Surfaces

An analysis of the two failed coatings applied previously showed that a high permeance of the coatings and the presence of pinholes in the coating were the primary cause of the failures. The two linings were made by two different coatings manufacturers. Both were approximately 65% solids by volume bisphenol A epoxies which had been applied in 3 coats to a total film thickness of 15 to 16 mils (400 microns). The high solvent content is the primary reason for the high permeance and likely contributed to pinhole formations as well due to entrapped solvent in the cured coatings.

To avoid these issues, an ultra-high solids coating, greater than 98% weight solids, with a very low permeance was investigated. This particular coating is a fiber-reinforced epoxy with a blend of discrete fibers. The fibers not only aid in physical reinforcement, especially in the critical flexural properties and crack resistance, but also greatly reduce permeance. Independent lab tests show a permeance reduction of more than 100-fold when the coating incorporates these particular fiber blends. To further ensure maximum chemical-resistance and minimum permeance, New Zealand Refining Company (NZRC) chose a novolak epoxy. Novolak epoxies have inherently better physical properties, lower permeance and generally better chemical resistance then other types of epoxies.