Behavior of Control and Inhibitive Polyaspartic Coatings Using Alkylammonium and Zinc Phosphate Corrosion Inhibitors in Soil

Abstract

This study is part of an anti-corrosion coating development project at CHEMSYSTEMS. The corrosion performance was assessed through erosion, immersion and soil corrosion experiments. The erosion results have previously been published. This article discusses the impact of soil on control polyaspartic coatings used to protect concrete and the modified polyaspartic coating intended to protect underground steel substrates. The modified polyaspartic coating was boosted with a micaceous iron oxide barrier, a liquid alkylammonium corrosion inhibitor, a powdered zinc phosphate corrosion inhibitor and a novel hardener. The surface finish of the steel samples was of a milled and blasted nature (SA 2.5). The coating was applied directly to the metal without the application of a primer or second layer of coating. The average thickness of the coating was 220±10 µm as a direct-to-metal protection system. The experiments were conducted in soil at room temperature (RT) and 35°C over 30 days. The experimental results of the control polyaspartic coating loaded on steel substrates exhibited severe blistering. The polyaspartic coating dispersed with a liquid alkylammonium inhibitor also exhibited blistering, whereas the modified polyaspartic coating with a zinc phosphate corrosion inhibitor showed an adequate degree of resistance to the impact of soil under the evaluated conditions. The results confirmed that the presence of a zinc phosphate corrosion inhibitor in combination with a micaceous iron oxide barrier improved the resistance of the coating to the evaluated soils in which it was positioned and at the investigated temperatures.

Immersion Corrosion Tests to Evaluate Polyaspartic Coatings on Steel

“…The hypotheses of the coating-degradation and protection mechanisms have been investigated [9] and are presented schematically in Figures 17 and 18. It can Figure 17: A schematic diagram of the control coatings [9] Steel substrate be seen that penetration of the corrosive environment through the unmodified polyaspartic coating is quicker as well as leads to the formation of blisters and rust on the steel surface.…”

“…The hypotheses of the coating-degradation and protection mechanisms have been investigated [9] and are presented schematically in Figures 17 and 18. It can Figure 17: A schematic diagram of the control coatings [9] Steel substrate be seen that penetration of the corrosive environment through the unmodified polyaspartic coating is quicker as well as leads to the formation of blisters and rust on the steel surface. The ,odified polyaspartic systems exhibited a good degree of protection as a direct-to-metal system on milled and blasted surface finished steel substrates, which is very beneficial in terms of site application by reducing the cost of the cleaning operation before coating that is normally recommended prior to applying a coating protection system.…”