Effect of benzotriazole on metal corrosion protection
February 27, 2023
The corrosion inhibition mechanism of benzotriazole is that the reaction group on the benzotriazole molecule interacts with the metal ions generated in the corrosion process to form a precipitation film or insoluble coordination film, and further polymerizes on the metal surface to form a precipitation protection film, thus preventing the corrosion process. Benzotriazole and its derivatives have unique and excellent corrosion inhibition properties for copper or copper alloys. Its corrosion protection mechanism is that in the solution of benzotriazole, copper replaces the hydrogen atom in the NH functional group of one benzotriazole molecule at the solid-liquid interface, connects with covalent bond, and connects with the free electron of nitrogen atom in another benzotriazole molecule to form a semi-permeable polymer complex.
The polymer complex film is stable and insoluble in many solvents, and has good corrosion resistance and protection. The anti-tarnishing protection of benzotriazole for silver or silver coating is also based on the formation of polymer complex film. Benzotriazole also has a good corrosion inhibition effect on zinc, cadmium, aluminum and tin, mainly due to the formation of a very thin surface precipitation film with zinc and cadmium plasma, which can effectively prevent zinc and cadmium from corrosion due to the formation of oxides on the surface. Generally, the benzotriazole is weighed by 1.5%~2% and placed in a container, and a little 95% ethanol is added to make it slowly dissolve in a small amount of ethanol, and then diluted with distilled water to 1.5%~2% benzotriazole aqueous solution for standby. If there are other added ingredients in the process formula, they should be dissolved in distilled water according to the measurement and mixed evenly for standby. Copper or copper alloy (such as brass, bronze, beryllium bronze, etc.) parts are subject to conventional degreasing, acid cleaning, neutralization and other processes to make the surface clean and bright. They can be immediately immersed in benzotriazole solution. The parts should be shaken repeatedly. After immersion for 3 minutes, they should be taken out, cleaned with clean flowing water, dried with compressed air, and dried at 60 ℃ for 15 to 30 minutes. If the temperature is too high to reach 100 ℃, the surface is liable to turn reddish brown and affect the appearance quality. Pay attention to the control temperature should not be too high, so that copper or copper alloy parts can obtain satisfactory corrosion protection effect. Application of benzotriazole corrosion protection (1) Copper or copper alloy parts are packaged with vapor phase antirust agent packaging paper containing 0.5% benzotriazole, and the storage period can exceed one year in industrial atmosphere. (2) Most of the antirust grease used at home and abroad are added with benzotriazole, the dosage is generally 0.05%~0.2%, and due to its poor oil solubility, it is often used to add such as n-butanol, sodium petroleum sulfonate, etc. as cosolvent to improve its corrosion inhibition and protection effect. (3) Adding 0.1% benzotriazole in lubricating oil can effectively protect copper and copper alloy parts, and prevent copper from catalyzing oil and causing oil deterioration. (4) In the mechanical cutting of copper or copper alloy, adding 0.05%~0.1% benzotriazole to the cutting coolant can effectively prevent discoloration and corrosion of parts during the machining process. (5) 0.4%~1% benzotriazole can be added to the coating when spraying copper or copper alloy parts, electroplating gold-like parts and spraying anti-discoloration organic coatings, which can effectively improve the corrosion resistance. (6) Dipping benzotriazole treatment after bright pickling or polishing of copper or copper alloy parts can replace chromate or chromate passivation treatment after pickling. For decorative plated parts such as brass plating and imitation gold plating, the corrosion resistance treatment of immersion benzotriazole solution can be used instead of traditional passivation treatment, which can significantly enhance the oxidation resistance and discoloration resistance of the coating and improve its corrosion resistance.
