# Environmentally Friendly Anticorrosive Polymeric Coatings
## 6 Applications  
According to ISO 12944-2:2017, the corrosive environments for steel structures are classified in three different categories, being: (i) atmospheric corrosion, (ii) immersed in water, and (iii) buried in soil. The corrosion stress of each environment is unique and generates different corrosion rates. This aspect indirectly determines the type of protective coating system needed for each category. The severity of the corrosion is classified according to its corrosion degree. In atmospheric environment, this scale goes from C1, which defines a very low corrosion level, to C5, for a very high level, and finally to CX for extremely corrosive environments. Table 1 summarizes the class definition together with the identification of the type of steel structures or applications that need a protective coating. The applications of anticorrosive coatings for class C1 and atmospheric environment are basically in heated buildings with clean atmospheres. Following the same rational, the class C2 is correlated with a low level of corrosion, which is usually found in metallic structures with a low level of pollution and unheated buildings where condensation may occur. The main applications of anticorrosive coatings immersed in water are found in river installation (e.g., hydroelectric power plants) for fresh water (Im1); and harbor areas with metallic structures like shuice gates, locks, jetties; and offshore structures for sea (or brackish) water environments (Im2). Antifouling paints are usually applied onto anticorrosive protective coatings in several immersed applications such as fuel-saving antifouling coatings for ships and net cages used in the aquaculture industry [98]. Finally, the main applications in soil environment are found in buried tanks, steel piles, and steel pipes (Im3); and those immersed assets with cathodic protection (Im4). Suitable anticorrosive coating solutions can be designed for any specific application. Owing to environmental concerns, eco-friendly coatings solutions for corrosion protection of metals are in high demand in almost all industrial sectors. The need for sustainable technologies capable of performing as well as traditional ones is particularly important for applications in highly aggressive environments such as coastal areas. Currently, there is a huge number of environmentally friendly anticorrosive marine coating technologies under research and in the development stage, among which the most important are:  
1. improved low-VOC (e.g., high-solids, solvent-free) and UV-curable coatings [99], and water-based coatings with better performance;
2. anticorrosive coatings incorporating bio-based polymeric resins [100] and natural compounds such as green corrosion inhibitors [101, 102];
3. addition of non-toxic compounds such as non-isocyanate [103] polyurethane-ureas (NIPUUs), non-toxic ion-exchange [104], graphene [86], or magnesium salts [105] as replacement for conventional toxic anticorrosives such as zinc, chromates, and zinc phosphate ones [106, 107];
4. biodegradable coatings [108];  
Low-VOC and solvent-free anticorrosive coatings are already widely used in marine (e.g., water ballast tanks of ships) and offshore industries. Epoxy coatings with a solid content between 70 and 100% are usually applied as primers and intermediates coats on ships [109], wind power structures [110], and oil and gas pipelines and platforms [65]. High solid PU coatings are also employed, but are preferred as topcoats, for atmospheric exposures due to their superior UV resistance. Topcoats for submerged zones are primarily applied to prevent biofouling, especially on ship hulls in order to minimize drag resistance and fuel consumption [109]. Moreover, biofouling is related to microbially influenced corrosion (MIC) [111], which is a serious issue for pipelines and submerged storage tanks since it can induce detrimental forms of localized corrosion [112]. The attachment of marine organisms also affects the performance of anticorrosion coatings.