The electrochemical corrosion behaviour of 22k gold (Au-5.8wt.%Cu-2.5wt.%Ag) and Ti containing 22k (Ti-22k) gold (Au-5.8wt.%Cu-2.0wt.%Ag-0.5wt.%Ti) was studied. Elemental Ti was added as the quaternary element to 22k gold by replacing Ag, resulting in the formation of secondary phase precipitates during age hardening treatment, thereby improving the hardness of the alloy. Anodic polarization tests were conducted for both 22k and Ti-22k samples in their as-cast annealed, cold-rolled annealed and age-hardened conditions using 0.9% sodium chloride and 1% lactic acid as medium. The as-cast and annealed 22k samples showed better corrosion resistance in both corrosion media whereas the 22k samples in the cold-rolled, annealed condition and Ti-22k samples in the as-cast, annealed condition showed poor corrosion resistance. After age-hardening treatment, cold-rolled Ti-22k samples showed better corrosion resistance due to the formation of passive layer (of TiO2) on the surface. However, corrosion gets initiated in the age-hardened Ti-22k due to the breaking and decomposition of the passive layer (TiO2) at a potential > 1.3 V.

中文翻译：

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22k金(Au-5.8wt.%Cu-2.5wt.%Ag)和含Ti的22k金(Au-5.8wt.%Cu-2.0wt.%Ag-0.5wt.%Ti)电化学行为研究

22k金（Au-5.8wt.%Cu-2.5wt.%Ag）和含钛22k金（Ti-22k）（Au-5.8wt.%Cu-2.0wt.%Ag-0.5wt.%Ag）的电化学腐蚀行为。 %Ti) 进行了研究。在22k金中添加元素Ti作为四元元素代替Ag，在时效硬化处理中形成第二相析出物，从而提高合金的硬度。使用 0.9% 氯化钠和 1% 乳酸作为介质，在铸态退火、冷轧退火和时效硬化条件下对 22k 和 Ti-22k 样品进行阳极极化测试。铸态和退火态的 22k 样品在两种腐蚀介质中都表现出更好的耐腐蚀性，而冷轧、退火条件下的 22k 样品和铸态、退火态的 Ti-22k 样品显示出较差的耐腐蚀性。经过时效硬化处理，由于在表面形成钝化层（TiO2），冷轧 Ti-22k 样品显示出更好的耐腐蚀性。然而，由于钝化层 (TiO2) 在电位 > 1.3 V 时破裂和分解，时效硬化的 Ti-22k 中开始腐蚀。