The role of formic acid and methanol on speciation rate and quality in the electrodeposition of chromium from trivalent electrolytes

IF 1.5 4区材料科学 Q4 ELECTROCHEMISTRY

Transactions of The Institute of Metal Finishing Pub Date : 1997-01-01 DOI:10.1080/00202967.1997.11871169

S. K. Ibrahim, A. Watson, D. Gawne

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引用次数: 20

Abstract

A successful enhancement of both the quality and the deposition rate has been obtained by the addition of some quantities of formic acid and methanol. The results were obtained by using very conventional conditions such as 25°C, no pH adjustment, low current density and very gentle agitation. An excellent quality of deposit with a deposition rate of 50-100 μm/hr was obtained. And sustained deposition up to 200 μm was achieved with prolonged electrolysis. The change in the chemical speciation of the electrolyte was studied by using Ion-exchange chromatography. A separation and identification of the various species, formed as the bath was aged with time, was obtained. The chromium concentration of each band was measured using the ICP spectrometer, monitoring the change in the concentration of the species with ageing. U.V. visible spectrometry was also used to confirm identification of the species. A clear correlation has been established between loss of deposition rate and the formation of higher oligomeric chromium (III) species. The role of methanol and formic acid in inhibiting this effect is discussed.

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甲酸和甲醇对三价电解液中铬形成速率和质量的影响

通过添加一定量的甲酸和甲醇，成功地提高了沉积质量和沉积速度。结果是在非常常规的条件下得到的，如25°C，不调节pH，低电流密度和非常温和的搅拌。沉积速率为50 ~ 100 μm/hr，沉积质量优良。通过长时间电解，可实现长达200 μm的持续沉积。用离子交换色谱法研究了电解液化学形态的变化。对随着时间的推移而形成的各种菌种进行了分离和鉴定。利用ICP光谱仪测量各波段的铬浓度，监测各物种浓度随老化的变化。紫外可见光谱法也被用来确认物种的鉴定。在沉积速率的损失和高低聚铬(III)的形成之间建立了明确的相关性。讨论了甲醇和甲酸在抑制这一效应中的作用。

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来源期刊

Transactions of The Institute of Metal Finishing 工程技术-材料科学：膜

CiteScore

3.40

自引率

10.50%

发文量

审稿时长

3 months

期刊介绍： Transactions of the Institute of Metal Finishing provides international peer-reviewed coverage of all aspects of surface finishing and surface engineering, from fundamental research to in-service applications. The coverage is principally concerned with the application of surface engineering and coating technologies to enhance the properties of engineering components and assemblies. These techniques include electroplating and electroless plating and their pre- and post-treatments, thus embracing all cleaning pickling and chemical conversion processes, and also complementary processes such as anodising. Increasingly, other processes are becoming important particularly regarding surface profile, texture, opacity, contact integrity, etc.