Anti-corrosion Coating Types and their Applications
This chapter covers the major types of coatings that are currently available for use and includes general information on the composition of coatings. It is intended to give basic information on coatings and is not a comprehensive guide to anti-corrosion coatings selection. The coating manufacturer is to be consulted if information on a specific product or coatings suitable for particular areas are required.Get more news about Anti Corrosion Coatings
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The types of anti-corrosion coatings used for OBM are often single pack products as this avoids the difficulties of measuring and mixing small quantities of two pack products, although small quantities of two pack products are sometimes available from paint manufacturers. Repairs carried out by the crew of vessels in service are rarely successful in the long term, due to the difficulties of preparing the surfaces to a sufficiently high standard.
In general, paints are either targeted for specific vessel areas and for specific functions for best performance, or universal coatings are available for all areas with a compromise in performance. In all cases, a balance between cost, performance and difficulty of maintenance has to be achieved. For example, anti-corrosive coatings used on the outside of the accommodation area have different performance requirements from anti-corrosion paints used in sea water ballast tanks as the corrosion stress placed on the latter is far greater. Ballast tanks are also much more difficult to maintain due to access difficulties and therefore the use of a highly effective (and often more expensive) coating is preferred to keep the steel in good condition.
In contrast, the holds of bulk carriers suffer from abrasion damage due to cargo impact and grab damage, which often leads to corrosion. Cargo holds used as ballast tanks during heavy weather can be particularly susceptible to corrosion at damage sites and a different coating is sometimes used for this cargo hold. This also applies to cargo tanks for oil carriers with a class notation for ‘Clean Products’, where any cargo tank may be used for heavy weather ballast.
Binders are the film forming components of paint which determine the principal characteristics of the coating, both physical and chemical. Paints are generally named after their binder component (e.g. epoxy paints, chlorinated rubber paints, alkyd paints, etc.). The binder forms a permanent continuous film which is responsible for adhesion to the surface and which will contribute to the overall resistance of the coating to the environment. Binders used in the manufacture of paints fall into two classes, thermoset and thermoplastic. A thermoset coating when dry will be chemically different from the paint in the can. Thermoset coatings are not affected by solvents once cured.
With a Thermoplastic coating, the dry film and the wet paint differ only in solvent content and chemically, these remain essentially the same. If the solvent originally used is applied to a thermoplastic coating, it will soften and can be re-dissolved in that solvent.