Sol–gel coatings for corrosion protection of metals

TLDR

Sol–gel derived films are promising alternatives to chromate pre‑treatments but suffer from high crack formation, limiting their corrosion‑protection performance. Incorporating organic components and inorganic nanoparticles into hybrid sol–gel coatings produces thicker, more flexible films with lower porosity and cracking, enhanced mechanical properties, and the possibility of self‑repairing inhibitor reservoirs.

Abstract

Sol–gel derived films exhibit a high potential as substitutes for the environmentally unfriendly chromate metal-surface pre-treatment methods. Inorganic sol–gel derived films offer good adhesion between metals and organic paint. However, they cannot provide adequate corrosion protection due to their high crack-forming potential. Introduction of an organic component to an inorganic sol–gel system leads to the formation of thicker, more flexible and functionalized films with enhanced compatibility to different organic top coatings. Incorporation of nanoparticles in the hybrid sol–gel systems increases the corrosion protection properties due to lower porosity and lower cracking potential along with enhancement of the mechanical properties. Furthermore, the incorporation of inorganic nanoparticles can be a way to insert corrosion inhibitors, preparing inhibitor nanoreservoirs for "self-repairing" pre-treatments with controlled release properties.