受BTA保护的白铜在模拟工业大气环境中的腐蚀行为

以涂盐沉积的方式进行室内加速实验,通过SEM/EDS、XRD和电化学测试等分析技术,研究受苯并三氮唑(BTA)保护的白铜在模拟工业大气环境中的腐蚀行为。结果表明,腐蚀初期受BTA保护的白铜表面存在棱状的盐结晶,说明腐蚀介质无法完全渗入基体。随着腐蚀时间延长,其对应的腐蚀电流密度呈现先减小后增大的趋势,其原因在于表面除了BTA化学转化膜还存在因腐蚀而产生的氧化膜,2者的共同作用延缓了腐蚀的进行,而当局部的BTA膜层因不断消耗出现破损,腐蚀区域则会从此处开始扩展,腐蚀电流密度也会随之增加。对比BTA处理前后的白铜,虽然最终的腐蚀产物主要成分均为ZnSO₄·6H₂O和Cu₄(SO₄)(OH)₆,呈现为疏松多孔状,但从截面形貌和动力学曲线分析,受BTA处理后的白铜腐蚀程度更轻微。

Corrosion Behavior of Copper-Nickel Alloys Protected by BTA in Simulated Urban Atmosphere

Copper-nickel alloys are extensively used in precision instruments, ship building, building decorations, and currency manufacturing because of their excellent mechanical properties, good corrosion resistance, and silvery metallic luster. However, they are likely to suffer from discoloration owing to corrosion in the polluted atmosphere containing SO₂. HSO3- and H+ exhibit ionization when SO₂ is adsorbed and dissolved in the thin liquid film on the surface of white copper. These sulfide-containing media will accelerate the corrosion process and affect the surface gloss. Benzotriazole(C6H5N3, BTA) is a corrosion inhibitor commonly used in Cu and its alloys that forms a chemical conversion film. It mainly protects the copper-nickel alloys in solutions containing Cl-or seawater polluted by sulfides. However, some studies have investigated the chemical conversion films of BTA that are affected by atmospheric pollution in the medium, especially focusing on analyzing their failure mode. This experiment was conceptualized based on the aforementioned problem. The corrosion behavior of the copper-nickel alloys protected by BTA in a simulated urban atmospheric environment was analyzed through SEM/EDS, XRD, and electrochemical tests. The laboratory experiments were accelerated by salt deposition. Results showed the presence of prismatic salt crystals on the surface of the copper-nickel alloy treated using BTA during the early stage of corrosion, indicating that the corrosion medium could not completely penetrate the substrate.The corrosion current density of the alloy protected by BTA will decrease first and then increase with the increasing corrosion time. This can be attributed to the oxidation and the presence of BTA chemical conversion films on the surface of the alloy;corrosion was delayed because of the combined action of these two factors. When the BTA film was damaged because of continuous consumption in the local area, the corrosion area expanded, increasing the corrosion current density. Be similar to the samples without BTA treatment, the final corrosion products of the samples treated with BTA were also loose and porous, and the main components were ZnSO₄·6H₂O and Cu₄(SO₄)(OH)₆. However, the degree of corrosion of the alloy protected by BTA was more slight according to the cross-section morphology observation and mass dynamic curve analysis.