Development of novel surface treatments for corrosion protection of aluminum: self-repairing coatings

Abstract

Two types of self-repairing coatings for the protection of Al and its alloys are reviewed: (1) organic coatings with capsules containing repairing agent and (2) porous anodic oxide films with inhibitor solution stored in the pores of the oxide film. First, polyurethane microcapsules containing liquid surface-repairing agents were synthesized and polyurethane coating with the capsules was painted on Al alloy specimens. After mechanical damage to the coating, self-repairing occurred by the reaction of water vapor in the air with the repairing agents released from the capsules. Second, porous-type anodic oxide films were formed on Al alloys, and the pores of the anodic oxide films were filled with inhibitor solutions, followed by application of a covering polyurethane layer. Inhibitors released from the pores efficiently protected the Al alloy substrate from corrosion arising from induced mechanical damage.

Development of self-healing coatings based on ethyl cellulose micro/nano-capsules

“…Various materials have been used as capsules shells encapsulating healing agents, such as urea-formaldehyde [10][11][12][13], poly(urea-formaldehyde) [14][15][16], melamine(urea-formaldehyde) [17,18], polyurethane (PU) [19,20] and epoxy resins [21,22] embedded in polymeric matrixes. Recently, the use of natural polymers receives considerable attention, especially because of their environmentally friendly character.…”

Self-Healing Coatings Consisting of an Outer Electrodeposited Epoxy Resin Layer and an Inner Porous Anodic Oxide Layer with Healing Agents for the Corrosion Protection of Al Alloys

“…The authors of this study recently developed self-healing polyurethane coatings with micro-capsules containing healing agents. The healing mechanism is similar to that described above [18,19]. In this case, the capsules consist of a polyurethane shell and a diisocyanate core [20,21].…”

“…This is discussed in Section 4.1. In previous studies, the authors of this paper found that a Cu 2+ /Cl − solution is significantly useful for detecting imperfections in oxide films on Al alloys [18,19,22,23]. Cu 2+ and Cl − ions synergistically enhance the local corrosion of Al alloys through imperfections.…”