Paint Application Processes

    In this section we will look at the advantages and disadvantages of different painting techniques.

    1. Hand Painting
    2. Airless Paint Systems
    3. Pressurized or Conventional Spray Guns
    4. Powder coating
    5. Dip coating
    6. Electrostatic Painting

    Hand Painting

    Hand Painting is an economical way to do small or specialized jobs such as a cabins or compartments, touch-ups of paint that has been damaged, or to coat entire decks with non-skid material. Hand and roller painting also cuts down on the need to mask off everything in the space.

    Painting a ship's decks and walkways can be a different story. This work often involves a crew of painters and can take hours to complete. When a large deck area is to be covered with non-skid it is a very demanding job. Weather must be considered and if the work is done in winter, temporary covers or tarps may be required, in addition to heaters to help the paint cure.

    The deck is first cleaned before being cordoned off to define boundaries. If the deck is new or if the existing coating is completely removed, the surface may be sandblasted to a level that is known as "white metal".  If the deck just needs patching, the area can be steam cleaned.  The primer and tie-coats may be sprayed on depending on their consistency, but if they are heavy or thick it may be necessary to hand roll.
    The non-skid material can be applied as part of the paint, or sprinkled on afterwards. 

    • The advantages to hand processes is that they allow for precision painting, and do not create atomized airborne particulate (although ventilation for fumes may be required depending on the area of work and the product being used).
    • The disadvantages are that hand painting is slow.

    If aesthetics are an issue, the final hand-painted surface may not be as smooth or consistent as other methods.  

    Airless Paint Systems

    Airless paint systems use a mechanical pump to force paint down a hose and out a gun. Unlike other spray guns that use compressed air, these systems rely on the pressure from the pump impeller to apply the paint.

    • Advantages to this type of system are that it has very low atomization, it can put a lot of paint quickly, and it will handle both heavy and light products with ease.
    • The disadvantage is that the clean-up is labour intensive, and there can be a lot of waste as the hoses and guns require a lot of paint to "prime" the pump system.

    The airless sprayer pattern can be more precise than some other systems, but because it forces paint onto a surface, more masking may be required than with brushes or rollers.

    Pressurized or Conventional Spray Guns

    The compressed air spray gun system was first used in the automotive industry in the early twentieth century when it was developed to spray lacquer onto cars on an assembly line. This type of system which uses compressed air to break up and atomize different paints and coatings, is used extensively in shipyards.

    A compressed air spray gun system can be run from either a large central compressor/air supply system or from portable compressors. For this reason the air pressure is monitored and there is also a regulator on the gun. Spray guns use "pots" or reservoirs that can be sized to ensure that the painter is using good ergonomics. 

    • The advantages of compressed air spray guns is speed of application, fast drying times, pattern control, and good coverage.  
    • The disadvantage is the excessive airborne particulate, and subsequent broadcasting of the VOC's.

    Some coatings dry or congeal very quickly in the gun so they must be cleaned out immediately to prevent costly blockages. Depending on the area to be covered, there can be a lot of masking associated with compressed air systems to avoid overspray. Ventilation and heat is often required to move air over the surface of the coating for drying and to remove fumes.

    Powder coating

    This system was developed to provide a very hard, durable surface and is used on marine and automotive equipment that will experience severe exposure. The process uses an electrically charged line to attract specialized paint in powder form, to the object being covered. The special thermoplastic or polymer based paints are then baked in a booth or oven to provide a tough outer skin that resists chipping or chafing.

    • Advantages to this type of paint system are the consistent finish and the durability and the absence of solvents which eliminates the VOC's associated with thinners.
    • The disadvantage of powder coating is that it is expensive to set up, and that the size of the object being coated is limited by the size of the curing booth.  For these reasons powder coatings are primarily used for ship components, rather than an entire vessel.

    Dip coating

    Dip coating is set up to completely immerse parts or components in a bath of liquid paint to provide protection from corrosion. A suitable sized vat is used and the object to be coated is then placed in the liquid.

    • The advantages of dip coatings are that they provide total coverage, and VOC's are not an issue.  Dip coating lends itself to production line work where multiple parts need to be coated.
    • The disadvantages are that dip coating can be slow and can require more drying time than spray finishes, due to the thicknesses of the coats. There is also an issue of masking or protecting studs, threads, or other surfaces that will need fasteners later on in the assembly process.

    Dip coating systems often require dedicated heat and ventilation to work properly. Dip coating systems are not typically used onboard ships, unless an extremely large component such as a main engine armature must be recoated in situ because it cannot be removed without cutting an access hole in the side of the vessel.

    Electrostatic Painting

    This process is similar to powder coating but the paint can be in powder or liquid form. Automated machines spray the product in the direction of the object that is electrostatically charged and as the paint accelerates toward the object and makes contact, it will completely encircle the component, sticking to the front, sides, and the back evenly. The trolley that moves the parts must be kept extremely clean to ensure the electrostatic charge is properly applied. The system is used for assembly line work and when the pieces are coated, they can either be left to air dry, or heated in a booth.

    • The advantages to this system are the evenness and speed with which the paint is applied. It is also environmentally friendly with filters capturing what little powder or liquid paint is not deposited.
    • The disadvantages are that the system is not portable and the size of components to be painted will be limited by the size of the booth.

    There is also a need to have all the parts and equipment fastidiously cleaned prior to entering this process as any contaminant on the parts will prevent adhesion.