Because of its good shielding and large specific surface area, graphene is easy to form dense film in the coating, which is of great help to improve corrosion resistance and attracts a lot of attention. A series of studies have shown that graphene grown on CVD can form a protective layer on the surface of copper, aluminum and other metals to prevent oxidation and corrosion of metals.
Reduced graphene oxide prepared with organic resin hybrid composites prepared by coating graphene, play shielding effect and excellent adhesion to resin, long-term preservation purposes, with the preparation of graphene coatings compared to conventional coatings, the corrosion rate of low alloy steel is reduced by 1 orders of magnitude. In addition to conventional corrosion protection, graphene can also react with hydrogen in metals to prevent hydrogen embrittlement. In addition, graphene can also improve the corrosion resistance of metals, and can also be used as a biological environmental protection layer.
At present, the application of graphene anti-corrosion coating is more mature graphite zinc powder heavy-duty anti-corrosion coatings, graphene anti-corrosion coatings in such heavy anti-corrosion mechanism is generally considered as follows:
(1) physical isolation.
Cl - has the characteristics of small ion radius, strong penetration, and can be strongly adsorbed by the metal surface. The two dimensional lamellar structure of graphene has a specific surface area of 2630m 2/g, which is layered distribution in the coating, forming a dense physical isolation layer, and has a good physical isolation function. Graphene is extremely dense, and even the smallest gas molecules can not penetrate, can effectively isolate Cl – penetration. Small size graphene can be filled into the coating defects, to a certain extent, to prevent and delay the molecular corrosion medium intruded into the metal matrix, enhanced the physical isolation of the coating.
(2) electrochemical protection.
The quality of zinc powder used in cathodic protection of epoxy zinc rich primer is only 20%~30%, and the remaining zinc powder is used as conductive medium. When the zinc powder is oxidized, it loses its electrical conductivity, and the coating loses its cathodic protection. Graphene has good electrical conductivity. Although zinc anticorrosive primer graphene greatly reduces the zinc content, but the film evenly dispersed graphene nanosheets to form a dense and continuous reticular layers of conductive structure, forming a conductive pathway and zinc zinc coatings in the lap, and activation, the coating on iron and steel base material to form a system of electrochemical loop to improve the cathode the protective effect of the coating.
Graphene epoxy zinc primer was prepared by replacing some zinc powder in epoxy zinc rich primer with graphene. The experimental results show that the zinc content of 47% mass fraction, dry film thickness of 100 m film, salt mist can reach 2500h, the scratch single expansion eclipse < 1mm, foaming, rust, cracking, spalling no scratches, corrosion resistance is higher than that of the high zinc content of zinc rich epoxy primer.