High performance and Environmentally Friendly Coating System for Water Ballast Tank of Ship in the Shipbuilding Industries

ABSTRACT
Paints are widely used in ship structure for corrosion protection. Anti-corrosion performance of paint is very important because it is closely related to ship’s safety and lifetime. IMO PSPC Guideline has recently been issued and, as a result, it is expected that quality of application of anti-corrosion paint is more tightly controlled and better quality is to be achieved.
In spite of positive points, the PSPC guideline is limitedly valid for currently used solvent-borne epoxy paint. Basically, there have been several considering points for the application of solvent-borne epoxy paint. Those are mainly quality of coating and environment. The solvent-borne epoxy paints contain large quantity of volatile organic compound (VOC) materials such as hydrocarbon solvents (e.g., Toluene and MEK). Those materials possibly cause degradation of coating quality by entrapment of solvent in the coating layer. Moreover, environmental pollution and hazard to health of workers are the most important considerations. Therefore, the current trend is toward the application of lower VOC paint or water borne paint for environmental and human protection.
In order to overcome such limits of solvent-borne paint, application of solvent-free paint is recommended. Solvent-free paint contains few amount of solvents (less than 5%) so it is very environmentally friendly. Another characteristic of solvent-free paint is build-up property, so thick paint film can be achievable with 1 coating instead of current 2 coatings
In this study, performance of solvent free paint has been evaluated comparing with performance of solvent-borne paint in terms of build-up properties and anti-corrosion properties. Build-up properties have been evaluated by sag resistance, edge retention ratio, holiday test, DFT distribution and so on. 4,200 hours of cyclic test (NORSOK M-501) has been carried out to evaluate corrosion resistance in addition to blistering test and water ballast tank simulation test.
From the test results, it would be suggested that the 1 main coating and 1 stripe coating of solvent-free paint replaces the current 2 main coatings and 2 stripe coatings of solvent-borne paint maintaining equivalent or higher performances.

Keyword: Solvent free paint, IMO PSPC, Cyclic test, VOC.