Currently, electrochemical plating, conversion coatings, anodizing, deposition of thin films (organic, inorganic or hybrid), laser surface alloying, cladding and organic coatings are employed to improve surface properties such as hardness or corrosion resistance. For example, the development of new “smart” coating systems implies not only mechanical covering of the protected surface with a dense barrier coating but also provides active properties which can allow continued physical or chemical protection, even after partial mechanical damage of the coating, by self-healing effects. In other cases, the active properties imply biological effects, by releasing of chemicals from “drug delivery” systems, or photoelectric effects due to doping the surface with adequate elements. These “smart” properties can be achieved by inclusion of specific additives into the coating system and can stimulate the superficial reactions after some damage. The sol-gel coating process is one of the most promising methods to create protecting coatings producing sensitive inorganic surfaces in general. In this environmentally friendly process, inorganic or inorganic-organic hybrid polymers are obtained by controlled hydrolysis and condensation reactions of molecular precursors. This article compares examples of the recent patents of active coatings and some of their important industrial utilizations.
Surface treatments, active coatings, hybrid polymers, sol-gel processes
Rio Grande do Sul Federal University, 90040-060, Porto Alegre/RS, Brazil.