When air drying is used in applying a layer of coating with one component for the purpose of providing protection for the surface may not suffice. These types of application rely greatly on solvent or water that is used to evaporate which results into a resin film that is not very good in resisting chemicals. This will only work if the coating used is polyurethanes that can have a reaction to air borne moisture and when that happens, the system will be a component of two.
Excellent chemical resistant coating are those systems that are made up of two components. The most common types of these coatings are vinyl esters resins, epoxy, methacrylate and polyurethane. These types have binder groups that use knitting or cross linking in order to make molecular strands that make up their structure. The cross linking is important because its density and degree is an indication of how hard and chemical resistant the coating is. There are exceptions such as in epoxy where its binder groups exhibit other characteristics which affect the chemical resisting ability.
There are different factors that determine how chemical resistant a coating is. Here is a list:
- the temperature
- the type of the corrosive medium
- the exposure time
- how concentrated a corrosive medium us
- how exposed is the coating to the corrosive medium
There are many types of resin available but the most commonly known to resist different types of chemicals are the following:
- Epoxy. Used to make floor coatings with high durability. It can withstand different chemicals such as salt, aqueous acids, oils, alkalis, sugar solutions, fats, lubricants and general fuels. They are more likely to be affected when exposed at a high temperature.
- Polyurethane. Also suitable for floor coatings because of its durability. It is resistant to aliphatic solvents, organic acids, fuel, hydraulic oils, alkalis and aromatic solvents. Resistance is higher compared to epoxy so steam cleaning can be used.
- Vinyl Esters. More common applications are lining on bund and tanks. It can resist almost every chemicals there is but the application must only be done by an expert.