Potentiodynamic studies on anodic dissolution and passivation of tin, indium and tin–indium alloys in some fruit acids solutions
Introduction
Tin and its alloys find widespread technological applications in the tinplate and electronic industry [1]. Tin coating of steel is extensively employed in the manufacture of food containers [2], [3]. The use of tinplate for food packing will result in some tin dissolving into the food content, particularly when uncoated internal surfaces are used [2], [4], [5], [6], [7]. Numerous studies have been focused on tin passivation in the presence of oxalic [8], maleic [9], tartaric [10], [11] and citric acids [12], [13], [14], [15], those are naturally present in the fruit juices and responsible for the electrochemical corrosion and/or passivation of tin [14]. So many publications on corrosion behavior of tin in some organic acids vis. Citric and maleic acids in aerated media were carried out [9], [13], [16]. Transparent conducting indium (III)-oxide thin film coatings are important in solar cells, especially in photovoltaic devices, which convert light into electrical energy.
In order to prevent pollution of the environment with lead, the use of lead will be limited in many parts of the world in the near future. In the electronics industry, efforts are now being made to develop a usable lead-free solder, and several tin-based alloys have already been proposed. The goal of the development of lead-free solder is to produce alloys with nearly the same properties as those of lead solder, and most research up to now has focused on melting point and physical strengths of alloys [17]. However, there is little information on the corrosion properties of base alloys for lead-free solder. The metals proposed for lead-free solder are tin–indium alloys.
There are not any data in the literature on corrosion behavior of tin or its alloys in malic acid solution. Malic acid is the active ingredient in many sour or tart foods. The salts and esters of malic acid are known as malates. Malates anion is an intermediate in the citric acid cycle along with fumarate. Therefore, the present work was undertaken to study the anodic behavior and corrosion of tin, indium and their alloys in malic and citric acid solutions at different temperatures. The work aims to investigate the composition of the passive layer formed on all investigated electrodes under their anodic polarization in the examined acids using XRD and SEM. The information obtained elucidates the role of the examined acids in the process of the anodic passivation on the investigated surfaces.
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Materials and solutions
Solutions (0.5 M) of malic (pH 1.98) and citric acids (pH 2.11) (analytical grade) were prepared by dissolving the appropriate weight in doubly distilled water. Tin and indium of high purity (99.999%) (Johnson Matthey Chemicals Ltd.) were used to prepare both Sn, In and Sn–In alloys as disk electrodes (A = 0.196 cm2) in a Gallenkamp muffle furnace using evacuated closed silica tubes at 700 °C for 24 h. The melts were shaken at every 6 h, to ensure the homogeneity of melting alloys and finally the
Behavior of tin
Fig. 1(a and b) shows the potentiodynamic polarization curves for Sn anode in 0.5 M solutions of malic and citric acid at different temperatures (30–60 °C). The polarization curves were swept from steady state of open circuit potential (Eo.c.p) up to +1500 mV (SCE). The data reveal that anodic polarization curves exhibit active–passive transition. The active dissolution region involves a well defined two anodic peaks (I and II), followed by a passive region, which extends up to +1500 mV (SCE) with
Conclusions
- 1.
Tin electrode showed two anodic peaks in both malic and citric acid, and the peak currents (Ip)I and (Ip)II increase while their corresponding peak potentials (Ep)I and (Ep)II are slightly shifted to more positive direction with increasing temperature. The active dissolution of indium involves two anodic peaks (I and II) in malic, and one peak only in citric acid. The two peaks (I and II) can be associated to the formation of InOOH and In(OH)3/In2O3 system, respectively. While the peak formed
References (28)
- et al.
Surf. Coat. Technol.
(2006) - et al.
Food Chem. Toxicol.
(1651) - et al.
Electrochim. Acta
(2000) - et al.
Anal. Bioanal. Chem.
(2002) J. Health Sci.
(2006)Anal. Chim. Acta
(1987)- et al.
Food Chem. Toxicol.
(1971) - et al.
Corros. Sci.
(1981) - et al.
Corros. Sci.
(2004) - et al.
J. Alloys Compd.
(2006)