What is Marine Paint Used for?
Transportation of goods by sea has historically been the most widely used form of shipping throughout human history. Though it cannot be compared to the speed of air shipping, it remains the preferred method for larger, heavier goods such as cars. It is also less expensive, less taxing on the environment, and there are virtually no restrictions on destinations. In short, it is nothing less than a driving force behind a functional global economy.
Keeping ships efficient is no small task. Coatings designed for this market are specifically formulated to ensure smooth sailing and as such are used for anti-fouling, anti-corrosion and self-cleaning purposes.
Marine coatings are waterproof, protective layers that are applied to surfaces exposed to or immersed in fresh, brackish, and/or salt water. They are used with boats, ships, yachts, ferries and other watercraft, as well as with marine platforms such as offshore oil rigs.
The application of marine coatings are quiet a plethora but we will mention a few that are majorly applied.
Marine paints are specifically used for watercrafts which are exposed and immersed into saltwater or freshwater. They are waterproof paints and act as a protective layer to the submerged materials. Generally used for ships, boats, ferries, yachts, submarines etc. Marine paint can also be used for houses. They can be used for hardwood floors, house furniture, exterior furniture etc.
Application of marine Coating
Marine coatings are primarily used in protecting the parts of marine vessels from corrosion and fouling. The paint system applied to any part of a ship will depend on the environment to which that part of the structure is exposed. Traditionally the painting of the external ship structure was divided into three regions.
- Below the water-line
Here is where the plates are continually immersed in sea water. The ship’s bottom has priming coats of corrosion inhibiting paint applied which are followed by an anti-fouling paint. Paints used for steels immersed in sea water are required to resist alkaline conditions. The reason for this is that an iron alloy immersed in a sodium chloride solution having the necessary supply of dissolved oxygen gives rise to corrosion cells with caustic soda produced at the cathodes. The paint should have a good electrical resistance so that the flow of corrosion currents between the steel and sea water is limited. These requirements make the standard non-marine structural steel primer red lead in linseed oil unsuitable for ship use below the water-line. Suitable corrosion-inhibiting paints for ships’ bottoms are pitch or bitumen types, chlorinated rubber, coal tar/ epoxy resin, or vinyl resin paints. The anti-fouling paints may be applied after the corrosion-inhibiting coatings and should not come into direct contact with the steel hull, since the toxic compounds present may cause corrosion.
2. The water-line or boot topping region
Here is where immersion is intermittent and a lot of abrasion occurs. Generally, modern practice requires a complete paint system for the hull above the water-line. This may be based on vinyl and alkyd resins or on polyurethane resin paints.
3. The topsides and superstructure
Exposed parts of ships to the atmosphere are often laden with salt spray, and subject to damage through cargo handling. Red lead or zinc chromate based primers are commonly used on superstructures. White finishing paints are then used extensively for superstructures. These are usually oleo-resinous or alkyd paints which may be based on ‘non yellowing’ oils, linseed oil-based paints which yellow on exposure being avoided on modern ships.
Where aluminium superstructures are fitted, under no circumstance should lead based paints be applied; zinc chromate paints are generally supplied for application to aluminium.
Temporal coating application for ship building
After the steel is blast cleaned it may be several months before it is built into the ship and finally painted. It is desirable to protect the material against rusting in this period as the final paint will offer the best protection when applied over perfectly clean steel.
The formulation of a prefabrication primer for immediate application after blasting must meet a number of requirements. It should dry rapidly to permit handling of the plates within a few minutes. It should be non-toxic and should not produce harmful porosity in welds nor give off obnoxious fumes during welding or cutting. It must also be compatible with any subsequent paint finishes to be applied. Satisfactory formulations are available, for example a primer consisting of zinc dust in an epoxy resin.
Good surface preparation is a prerequisite for a successful painting,the primary cause of many paint failures being the inadequacy of the initial material preparation. It is particularly important before painting new steel that any mill scale should be removed. Mill Scale is a thin layer of iron oxides which forms on the steel surface during hot rolling of the plates and sections. Not only does the non-uniform mill scale set up corrosion cells as illustrated previously, but it may also come away from the surface removing any paint film applied over it.
Marine Paints may contain toxic or irritant substances, and the solvents may give rise to flammable and potentially explosive vapours which may also be toxic to our health. Personnel using such paints should be warned of the particular risks arising from their use. Paints containing organic pesticides can be particularly dangerous. If the manufacturer's instructions are not given on the container, information should be obtained at the time of supply about any specific or general hazards concerning the product and also whether special methods of application should be followed. Such advice should be readily available at the time of use but the following precautions should always be adhered.
Protecting ships with good marine coatings can be tedious and complex. For more assistance, information, consultation, training and procurement contact us.