Isocyanate Free Water Repellent Top Coat For Offshore Corrosion Protection

摘要

To obtain long term corrosion protection in demanding offshore environments the coating system needs to protect the structure from water to prevent corrosion. We have developed a durable isocyanate free top coat that can actively repel water to provide outstanding protection for offshore steel structures from corrosion.In this paper, the development of a water repellent, isocyanate free top coat is described and the effect of this top coat is compared to conventional coatings. The top coat is tested in a single coating system, applied directly to metal (DTM) and in a two coat system with a zinc rich primer.In order to evaluate performance of the coating systems, a range of anticorrosive and mechanical tests are carried out for the top coat both in one coat and two coat systems. Salt Spray (ISO 9227), Blister Box (ISO 6270-1) and Ageing Cycling Resistance (ISO 12944-9) tests are conducted to compare the water permeation and corrosion resistances of the coating systems. Adhesion of the top coat to steel and the zinc rich primer is evaluated by Pull Off Adhesion test (ISO 4624). Mechanical properties of the coatings are evaluated by Mandrel Flexibility (NACE Standard TM0304 Section 12), Impact (ISO 6272-2), and Thermal Cycling Resistance (NACE standards TM0304-2004 and TM0404-2004 Section 9, but using different type of panels) tests.The one coat system with the water repellent top coat (DTM application) have shown remarkable corrosion creep and adhesion retainment results after 1440 hours exposure in Salt Spray test (ISO 9227). Blister Box test (ISO 6270-1) results indicate robust water permeation resistance in humid conditions. Ageing Cycling Resistance (ISO 12944-9) test results have shown that two coat system with activated zinc rich primer and the water repellent top coat possesses robust anticorrosive properties and outperforms conventional three coat system. The preliminary test results show how incorporation of active water repellence into the top coat greatly enhances the ability of the coating systems to reduce corrosion in an offshore environment.