Introduction
This chapter covers the main types of coatings currently available for use and provides general information about the composition of coatings. It aims to provide basic information on coatings and is not a comprehensive guide to the selection of Anti corrosion coating . If you need information on suitable coatings for a particular product or area, you need to consult a coating manufacturer.
Coatings are often divided into two broad categories:
Products for application in new buildings and;
Friendly products for maintenance and repair, including both major renovations and onboard maintenance (OBM).
The types of Anti corrosion coating used for OBM are often single pack products as they avoid difficulties in measuring and mixing two-pack products, although small pack products are sometimes available in small quantities from paint manufacturers. Repairs made by service ship crews are rarely successful in the long run because of difficulties in producing sufficiently high-quality surfaces.
In general, paints are either targeted for specific vessel parts and specific functions for optimal performance, or universal coatings are available for all areas where performance is compromised. In all cases, there is a balance between cost, performance and maintenance. For example, Anti corrosion coatings applied to the exterior of a dwelling require a different performance than rust-resistant paints used in marine ballast tanks because the corrosion stress applied to the latter is higher. Ballast tanks are more difficult to maintain due to access difficulties and therefore it is preferred to use a highly effective (and often expensive) coating to keep the steel in good condition.
In contrast, the impact of freight and the forcible damage cause a large amount of friction damage to the conductor’s holdings, which often leads to rust. Cargo holds used as ballast tanks in heavy weather are particularly susceptible to corrosion in damaged areas and a separate coating is sometimes used for these cargo holds. This also applies to cargo tanks for oil carriers with class notation for ‘clean products’, where any cargo tank can be used for large weather ballast.
Paint Composition
Paint can be described as a liquid substance that can be applied or spread on a solid surface on which it then dries or hardens to form a continuous, sticky, film. Paint basically consists of three major components and numerous repeat derivatives that are included in small quantities. The main components are:
Binder (also called vehicle, medium, resin, film or polymer)
Pigment and extender
Solvent
Only the first two of these make the final dry paint film. The solvent is only necessary for the use of paint and to help in the formation of the initial film, but not necessarily, some solvent is always put into practice depending on the level of ventilation.
Binders
Binders are film-forming elements that determine the main properties of a coating, both physical and chemical. Paints are usually named after their binder components (e.g. epoxy paints, chlorinated rubber paints, alkyd paints, etc.). The binder forms a permanently intact film that is responsible for sticking to the surface and which contributes to the overall resistance of the coating to the environment. Binders used in the manufacture of paints fall into two classes, thermosets and thermoplastics. Once dry the thermoset coating will be chemically different from the paint in the can. Thermoset coatings are not affected by solvents once cured.
Cross-linked (Thermoset) Coatings
These coatings are usually supplied in two separate packs that are assembled immediately before application. In liquid paints where the solvent is included, drying is considered a two-stage process. The two phases actually come together but at different rates.
Stage One: Solvent is lost from the film by evaporation and the film becomes dry to touch.
Stage Two: The film progressively becomes more chemically complex by one of the following four methods:
Reaction with oxygen in the atmosphere, which is called oxidation.
Reaction with additional chemical treatment agents.
Reaction with water (atmospheric moisture).
Artificial heating.
This change in paint is known as drawing or curing. The films formed by the above methods are chemically different from the original binders and will not re-dissolve in their original solvent.
Epoxy Resins
These resins are especially important and their use as a binder was one of the most significant advances in Anti corrosion coating technology. The rate of cross-linking or curing depends on the temperature. The treatment rate of standard epoxy below 5C is significantly reduced and complete curing is required to obtain optimal film properties. Epoxy will be cured with special curing agents or set at a temperature of -5C. To ensure that the coatings are effective in service, it is necessary to strictly follow the recommendations on the application temperature of the coating manufacturer. More information about then Visit (anti corrosion coating manufacturers and suppliers) - http://www.protexion.in/anticorrosion-protective-coatings.php
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