Study of Mixed Flowing Gas Exposure of Copper

Abstract

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.

Laboratory scale investigation into the corrosion of copper in a sulphur-containing environment

“…At 80 °C parabolic rate behaviour was observed, with a thickness loss rate that decreased from 0.07 µm/min in the first hour to 0.02 µm/min at the end of the second hour. This parabolic rate behaviour observed at 80 °C can presumably be attributed to the critical thickness effect observed by Reid and co-workers [22]. According to these authors the rate of film growth becomes parabolic when the corrosion product reaches a critical thickness, which indicates that diffusion of copper through the corrosion layer becomes rate-limiting as the corrosion scale becomes thicker.…”

“…Each of the three tests would display unique effects which is typical of what might happen with long exposure times, as in the PGM smelter. Other factors affecting corrosion behaviour of a scale includes morphology of the corrosion product (porosity, grain size and permeability), loss of the protective layer due to poor adherence [15], defects [22] and internal stresses which lead to crack formation [11]. These factors may induce linear rate growth of the corrosion layer at long exposure times.…”

“…A number of authors have however, studied phase relations between copper and sulphur, chlorine and H 2 S at low temperatures [10][11][12][13][14][15][16][17][18][19][20][21][22]. Bartkowicz and Stoklosa established that the sulphidation of copper between 97 °C and 150 °C is complex, with the formation of hexagonal chalcocite (Cu 2 S), monoclinic chalcocite (Cu 2 S) and covellite (CuS) [12].…”

“…Chlorine has the ability to diffuse through the corrosion layer, providing a path for metal ion diffusion to the reaction surface. Chlorine therefore increases the corrosion rate by physically disrupting the protective scale [20][21][22]. The objective of this study was to determine how the surface temperature of copper and the composition of the corrosive gases affect the corrosion rate of copper, as well as the phase compositions and morphologies of the corrosion products.…”

Crevice Corrosion Resistance and Structure of Passive Film on Fe–Mn–Si–Cr–Ni Steel

“…Recently, the Focused Ion Beam (FIB) method has been proposed to solve this problem. [13][14][15][16][17] By using this FIB method for samples, TEM -EELS 18) was additionally applied to analyze the chemical state of the passive film of the steel. Thus, in -situ observation can be applied for the…”