Analysis of Films on Copper by Coulometric Reduction

Cu corrosion in mixed flowing gases (MFG) has been widely studied. However, most of these studies have been carried out using conditions which were designed for accelerated tests simulating North America and Western Europe. More and more equipment are being deployed to emerging markets such as Asia Pacific and China, Eastern Europe, and the Middle East, where they are subjected to much more corrosive environments than those typically seen in North America and Western Europe. There is a need to understand the corrosive conditions in the emerging markets and come up with an accelerated test for products to be deployed in those conditions. In this work, we investigated the corrosion products on test Cu coupons exposed to harsh conditions by a combination of several analytical techniques. This work allowed us to establish a procedure for quantifying corrosion products and led to insights about corrosion mechanisms for copper in highly corrosive environments. Results showed that the corrosion of copper in the highly corrosive MFG testing condition (containing normalH2S , SO2 , Cl2 , and NO2 ) leads mainly to the formation of copper sulfide (Cu2S) at the exposed surface, with the presence of a thin, buried cuprous oxide (Cu2O) layer sandwiched between Cu2S and copper substrate. The thickness of the corrosion products increases linearly with the exposure time.

Section: C31mentioning

confidence: 95%

Corrosion of Cu under Highly Corrosive Environments

Demirkan

Derkits²,

Fleming³

et al. 2010

“…There are conflicting views regarding the order of reduction of Cu corrosion products, in particular Cu oxides. [14][15][16][17] However, convincing evidence presented by Nakayama et al, on differently prepared samples of Cu oxide films, demonstrated that CuO ͑plateau I͒ is first reduced in 0.1 M KCl, followed by the reduction of cuprous oxide ͑Cu 2 O͒ ͑plateau II͒. 18 The reduction of the Cu 2 O is additionally complicated by the reduction of covellite ͑CuS͒, which occurs in the potential region of Cu 2 O ͑plateau II͒.…”

Section: Methodsmentioning

confidence: 99%

Study of Mixed Flowing Gas Exposure of Copper

Reid¹,

Punch²,

Garfias-Mesias³

et al. 2008

This paper describes the results of copper coupons exposed to a class III mixed flowing gas environment ͑MFG͒ following the guidelines given by the Battelle Laboratory and the International Electrotechnical Commission for environmental testing. Corrosion products were studied in detail using scanning electron microscope, energy dispersive X-ray spectroscopy ͑EDS͒, X-ray diffraction ͑XRD͒, focused ion beam ͑FIB͒, secondary ion mass spectroscopy ͑SIMS͒, and transmission electron microscope. The weight gain measured after each exposure was compared with the weight gain calculated from the cathodic reduction of the corrosion layers and cross sectioning using an FIB. The result shows a relatively good correlation between the measured and the calculated experimental values of weight gain. As expected, within the first week, the different corrosion layers thickened until they formed a thick layer that became the determining step for further growth. After several days of exposure the Cu coupons developed a complex multilayered structure consisting of cuprous oxide ͑Cu 2 S͒, cupric oxide ͑CuO͒, copper sulfide ͑Cu 2 S͒, covellite ͑CuS͒, and evidence of antlerite ͑3CuO SO 3 2H 2 O͒. No Cl-containing corrosion products were identified using XRD. However, EDS and SIMS analysis showed that Cl was distributed throughout the corrosion products, indicating that although Cl is inside the corrosion products, it is not part of the crystalline structure. Also, this suggests that Cl plays an important role in accelerating the corrosion of Cu during exposure to the MFG class III test. In the early 1980s, with the discovery of significant printed wiring board ͑PWB͒ and component failure modes ͑mainly due to corrosion͒, a number of firms and laboratories set out to develop accelerated corrosion test methods with a known acceleration factor. The aim of such efforts was to shrink years of service into days of testing, and prove that the field failure modes would be replicated during the tests. The PWB and its components were exposed to different levels of a mixture of gases, temperature, and relative humidity, which would simulate the environment during operating conditions. IBM, AT&T, and Battelle Laboratories participated in this effort.1 The result of this work was the development of a mixed flowing gas ͑MFG͒ test, which is primarily a laboratory test in which the temperature, relative humidity, and concentration of gaseous pollutants are carefully defined, monitored, and controlled.

“…The reason for the use of these electrolytes is probably for the relative stability of Cu 2 O in less alkaline solutions. 10 In the ASTM 13 and Japan Copper and Brass Association ͑JCBA͒ 11 the CP method with 0.1 M KCl has been recommended as a standard method for selective determination of Cu 2 O and CuO. However, when the solution alkalinity is low, the separation between the reduction waves of the two oxides is not sufficient, as also shown below in this paper.…”

mentioning

confidence: 87%

“…The reduction of oxides using neutral or weak alkaline solutions, including 0.1 M KCl, [9][10][11][12][13][14] 0.1 M NaHCO 3 , 18 0.1 M Na 2 CO 3 , 8,17 and 0.1 M Na 2 B 4 O 7 , 7,22,23 have usually been performed for the electrochemical characterization of copper oxide films. The reason for the use of these electrolytes is probably for the relative stability of Cu 2 O in less alkaline solutions.…”

mentioning

confidence: 99%

Which Is Easier to Reduce, Cu[sub 2]O or CuO?

Nakayama

Kaji

Shibata

et al. 2007

Chronopotentiometry ͑CP͒ using 0.1 M KCl as the electrolyte has been most frequently used for selective determination of cuprous and cupric oxides ͑Cu 2 O and CuO͒ formed on copper surfaces. However, there are conflicting views regarding the order of reduction of the oxides. This study was carried out to settle this problem. Differently prepared samples of Cu-duplex oxide films were partially reduced by means of CP with 0.1 M KCl and then submitted to X-ray diffractometry and also linear sweep voltammetry using a strongly alkaline electrolyte ͑6 M KOH + 1 M LiOH͒ in which reduction peaks of Cu 2 O and CuO could be obtained with good separation. The results clearly demonstrated that CuO was first reduced in 0.1 M KCl, followed by the reduction of Cu 2 O. However, the reductions of both oxides were found to occur simultaneously, to a greater or lesser extent, in 0.1 M KCl. It was also revealed that CuO was reduced to metal Cu in one step and that a partially reduced Cu-duplex oxide sample had an expected Cu͉Cu 2 O͉Cu sandwich structure.Oxide films on copper are composed of cuprous oxide ͑Cu 2 O͒ and/or cupric oxide ͑CuO͒. 1 Selective determination of the two oxides with different properties is important for corrosion characterization. Surface analytical techniques, including X-ray photoelectron spectroscopy ͑XPS͒, 2-4 Auger electron spectroscopy ͑AES͒, 4 X-ray diffraction ͑XRD͒, 5 and infrared reflection absorption spectroscopy ͑IRAS͒, 6,7 have been used for this purpose. These spectrophotometric techniques are useful for qualitative analyses but not necessarily adequate for quantitative analyses.Electrochemical techniques, including chronopotentiometry ͑CP͒ and linear sweep voltammetry ͑LSV͒, provide reliable information on the "quantities" of copper oxides, which can be accurately obtained from the quantity of electricity required for the reduction of oxides. CP has been most frequently employed for simultaneous determination of Cu 2 O and CuO formed on copper surfaces. However, there are conflicting views regarding the order of reduction of oxides. Miler, 1 Pops and Hennessy, 8 and other authors 9-14 have claimed that the reduction of Cu 2 O occurs first, followed by the reduction of CuO. However, no convincing evidence seems to have been presented. Several authors have proposed that CuO is first reduced. 15-19 Su and Marek 18 proposed a two-step reaction mechanism in which the reduction of CuO to Cu 2 O occurs first and both the generated Cu 2 O and the originally existing Cu 2 O are then reduced together.In 2003, a subcommittee on the cathodic reduction of copperoxide films was constituted in the Japan Society of Corrosion Engineering ͑JSCE͒ ͑of which two of the authors, S. Nakayama and T. Notoya, are members͒, and round-robin experiments were performed to determine which mechanism is valid in the cathodic reduction of Cu-duplex air-formed thin oxide films. In the committee's reports, 20,21 it was concluded that in CP measurements with 0.1 M ͑=mol dm −3 ͒ KCl as the supporting electrolyte, CuO was first reduce...