When choosing a suitable painting system which guarantees effective anti-corrosion protection, the following factors need to be considered:
- corrosion aggressiveness of the environment where goods will be exposed
- durability of the painting system
- type of the material painted
- painting costs in the 'life cycle' of the construction.
The PN-EN ISO 12944-2 norm describes six atmpspheric corrosivity categories (C1 – C5M) and three categories of corrosive conditions in immersion lm 1 – lm 3). While choosing the corrosivity category for the project, not only final conditions should be taken into account but also transport and storage before final fitting of the construction.
The durability of the painting system is the period counted from the first application to the moment of the first renovation. The PN-EN ISO 12944 norm distinguishes 3 durability periods:
- Low (L) 2–5 years
- Medium (M) 5–15 years
- High (H) over 15 years
Planning the painting system primarily involves the right choice of paint layers to protect the surface. The coating may consist of one paint applied in one or more layers. However, generally a few various paints constitute the final protective coating system.
Types of paints are often referred to according to the order of application, for instance, primer, undercoat, topcoat. The anti-corrosion mechanism is based on high electric resistance, anti-corrosion pigments and cathodic protection. Various layers of the system may protect surfaces in different ways, for instance the topcoat may reveal high electric resistance, but the primer may contain anti-corrosion pigments.
Paints consist of resin, pigments, solvents and additives and can be categorized according to many different criteria, but generally they are classified depending on the type of resin used and the drying method. The table below presents various paint types: