Copper is one of the earliest metals discovered by humans. It is slightly hard, extremely tough, wear-resistant, and has good ductility. It has good thermal and electrical conductivity and is widely used in electrical, light industry, machinery manufacturing, and construction industries. , Defense industry and other fields, second only to aluminum in the consumption of non-ferrous metal materials in China. Copper and copper alloys are also very important materials in the marine industry, and have been widely used in seawater desalination plants, marine oil and gas production platforms, and other coastal and subsea facilities. Copper and some of its alloys have good corrosion resistance and are stable in dry air. However, a layer of green basic copper carbonate can be formed on the surface in humid air, commonly known as copper green, which is easily eroded by alkali.
In order to improve the corrosion resistance of metal materials and enhance the adhesion between organic coatings and metal surfaces, various pretreatment methods and processes for metal surfaces have been developed. In the traditional metal surface pretreatment process, the most widely used is phosphating and chromate passivation treatment. However, these two technologies have the disadvantages of high pollution and high toxicity. As society attaches great importance to environmental issues, the use of these two technologies is gradually being restricted and is on the verge of being banned. At present, organosilane metal surface treatment technology is considered to be the most promising one. This technology uses silane reagent (the general formula is X-Si (OR) n, where X represents a functional group, R is an alkyl group, usually R is -CH3 or -C2H5, n = 2 or 3) to generate silanol (X-Si (OH) n), silanol combines with the metal surface and crosslinks itself to form a dense protective film on the metal surface. However, in actual research, it was found that it is difficult to form Si-OM bonds on the copper substrate, which results in poor treatment of the copper substrate with general organosilanes.
Researchers from the Ningbo Key Laboratory of Marine Protection Materials and Engineering Technology, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences used ordinary epoxy-functional silane coupling agents as raw materials and synergistically enhanced them with thiourea (TUA) to obtain a copper matrix. Passive coating with excellent effect. The results of the study show that the combination of the silane coating and the copper matrix is ​​significantly improved after TUA reinforcement. The electrochemical impedance spectroscopy shows that the corrosion resistance of the silane coating is also significantly improved after the addition of TUA. The strengthening mechanism of TUA is that on the one hand it can crosslink epoxy groups to improve the physical barrier effect of the silane coating; on the other hand TUA and copper have a strong interaction, improving the bonding performance of the silane coating and the copper matrix.
The passivation coating is simple to prepare, uses water as a solvent, has a low price, and has a very good application prospect. The relevant research results were published in Surface and Coatings Technology (2012, 213: 175-192). The team has also made some other progress in metal surface treatment and applied for a national invention patent (application number .9).
The above research work was supported and supported by the Zhejiang Innovation Team (2011R50006) and other projects.
Cross-section morphology and anti-corrosion performance of copper silane coating before and after TUA reinforcement
Copper impedance test results before and after TUA enhancement
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