Types of coatings
Coatings are specified as organic or inorganic according to the nature of their binder. Organic coatings are those that have an organic binder. Inorganic coatings are those that have an inorganic binder such as a silicate.
Organic coatings are often liquid or powder paints that require several layers before a thick enough coating is achieved to inhibit corrosion. The coating must be dense and durable.
These coatings are based on carbon containing materials normally derived from refined and/or modified petroleum products, as well as different solvents/water, pigments, additives, and fillers.
Below are four organic coatings commonly used in industrial applications:
- Polyurethane coatings – Enhanced with specialty additives, polyurethane coating products are characterized by exceptional resistance to corrosion, abrasion, chemicals and weathering processes. Due to this versatility, you will find polyurethane used as a primer, intermediate coat or a topcoat depending on the needs of the application.
- Epoxy coating systems – Epoxies define a large group of coating products, with excellent film-building, mechanical and chemical properties. Epoxy coating systems can bond to different surfaces. This makes them optimal choices for many industrial painting projects that demand maximum protection against normal wear and tear, abrasion, corrosion, moisture, water, salt air, fuels and chemicals, as well as non-oxidizing acids, alkali and salts in immersion. The most notable limitation of the epoxy family of coatings is their poor performance in sunlight.
- Alkyd coatings – Alkyd coatings can be applied to prepared substrates in various environments. They are mostly used for decorative purposes and for the protection of steel exposed to relatively mild environments. They are available in one-pack product. On the downside, alkyds use oxygen in order to complete the chemical reaction that turns them into durable finishes. Since oxygen needs to disperse throughout the paint film, these coatings take longer to dry compared to other products.
- Polyester coatings – Although not exclusive to coil coatings, amino cross linked polyesters are a predominant chemistry in that technology. There is an almost infinite variety of polyesters that can be used because there are a number of difunctional and trifunctional glycols that can be used in combination with aromatic, aliphatic and cycloaliphatic diacids. Variations in functionality and molecular weight allow primers and topcoats to be formulated such that corrosion resistance and UV/moisture durability can be manipulated along with formability.
All those technologies are available in Solvent borne and Waterborne systems.
Inorganic coatings encompass surface conversion, anodizing, enamelling, metallic coatings and more. These coatings are created through a chemical action that changes the surface layer of metal into a metallic oxide film or compound to reduce corrosion.