Cost Effective corrosion protection of ballast tanks using heavy duty glassflake coatings

摘要

The corrosion problems associated with ballast tanks have been well documented by a number of sources. These problems occur not only in seawater ballast but also within other cargo/ballast tanks where it is normal for some seawater to be present. The seawater often combines with dissolved gases including H_2S and CO_2 to create acidic and very corrosive conditions. There are period where tanks are empty, allowing unhindered access to oxygen and combined with wet dry cycling aggressive corrosion within the tanks is the inevitable consequence. Unless appropriate preventive measures are put in place, corrosion will seriously affect the structural integrity of the steel. Other areas of corrosion include the void spaces and associated valves, pipework and process equipment. The types of corrosion found within ballast and ballast/cargo tanks, include: pitting corrosion, concentration cell corrosion, uniform corrosion and stress related corrosion effects caused by welding and the increased usage of high tensile steel during construction. Microbiologically induced corrosion also exists in a large number of tanks. Standard rates of corrosion due to uniform corrosion would typically be 150 to 1,000 microns per year, with pitting corrosion in seawater service of up to 2.5 mm per year.