Marine paints and coatings: how to specify and order them

What types of marine paint does a ship buy?

A ship buys paint by job: primer and anticorrosive coats for bare steel, topcoats for the finished colour and weather resistance, antifouling for the underwater hull, and special coatings for hot surfaces, tanks and decks. Each job has its own product, and the maker's data sheet says which coats go together.

• Primers and anticorrosive coats are applied first to prepared steel to protect it from rusting.
• Topcoats give colour, gloss and resistance to sun and weather on the hull above water, superstructure and funnel.
• Antifouling is applied below the waterline to discourage marine growth on the hull.
• Heat-resistant coatings are for hot surfaces such as exhaust pipes and funnel casings.
• Tank coatings are for ballast, cargo or water tanks. The product depends on what the tank holds, so say so in the enquiry.
• Deck paints are made for walkways and decks, where wear and slipperiness matter.
• Thinners and hardeners are separate items. A two-pack paint is useless without its own hardener, and the thinner should be the one the maker names.

What should you know about antifouling rules?

Antifouling is regulated. The IMO's AFS Convention prohibits harmful organotins, including TBT, as biocides in antifouling paints on ships. Its 2021 amendment also bars cybutryne, a biocide, in systems applied from 1 January 2023. Rules on biocidal products can change, so confirm the current position with the paint maker and your flag administration before ordering.

State the vessel's flag, trading area and the date of the last docking in your enquiry. This lets the supplier propose a product that the maker lists for that use.

How is a marine paint specified?

A paint is specified by the maker's product name, the colour code, the pack size and the number of components. The data sheet gives the technical figures, and the same terms appear on every maker's sheet.

• Volume solids (%): the share of the wet paint that stays on the surface as dry film.
• Dry film thickness (DFT, micrometres): the thickness of the dried coat the specification asks for.
• Theoretical spreading rate (m² per litre): roughly 10 × volume solids (%) ÷ DFT (µm). A paint with 50% volume solids applied at 100 µm DFT covers about 5 m² per litre in theory. Real coverage is lower because of waste, surface roughness and weather.
• Pot life: how long a mixed two-pack paint stays usable. It shortens when it is warm.
• Overcoating interval: the minimum and maximum time between coats. Both are given at stated temperatures.
• One-pack or two-pack: a two-pack product comes as base and hardener that must be mixed in the stated ratio.
• Colour code: the maker's own colour name or number, sometimes with an RAL or similar reference.

Divide the area by the spreading rate for a rough litre quantity, then add the allowance your superintendent or the maker recommends.

How are marine paints sold and counted?

Paint is sold in cans or tins of a fixed size, and IMPA section 25 lines are normally counted in CAN. Pack sizes differ between makers, so quote the litres per can and the number of cans, not only litres.

Order by the maker's product name and colour, because two paints that look alike can have different chemistry and cannot be mixed. A generic request such as "red oxide primer, 20 L" may be answered with a product that does not match the coat already on the hull. If you do not have the product name, send the old can label or the data sheet.

What should you check before ordering?

Check the surface preparation, the existing coating system and the storage conditions. The data sheet names the surface standard the coat needs, usually a blast or power-tool cleanliness grade as defined in ISO 8501-1, which uses grades such as Sa 2½ for blast cleaning and St 2 or St 3 for tool cleaning. Check the exact grade on the data sheet of the product you want.

Also confirm:

• the coating already on the surface, and whether the new coat is compatible with it
• the temperature and humidity at the place of work
• the shelf life and storage temperature, taken from the data sheet, so cans are not left to expire in the paint locker
• whether the maker lists a separate thinner and cleaner for the product

Is paint dangerous cargo?

Many paints, thinners and hardeners are flammable liquids and travel as dangerous goods. The IMO's IMDG Code covers packaged dangerous goods carried by sea, including packing, stowage and segregation. The maker's safety data sheet gives the classification for each product.

Tell the supplier early if the paint must be delivered to a ship at anchor or by air, since dangerous-goods rules affect which routes are possible. Ask for the safety data sheet with the quotation and keep it with the ship's stores records.

How do paint types compare?

Where do paint and painting equipment sit in IMPA?

In the IMPA marine stores guide, section 25 is Marine Paint and section 27 is Painting Equipment: brushes, rollers, spray guns and similar items. In ShipsBay these are the Marine Paint and Painting Equipment categories. Section numbers are a search aid; the paint is still ordered by product name.

Start by searching the catalogue for marine paint or paint brushes. If you already have a list of product names, colours and can counts, send an RFQ as a document. For the general steps of a clear enquiry, read how to prepare a ship stores RFQ, and see what an IMPA code is for the numbering.