Influence of pH and Chloride Concentration on the Corrosion Behavior of Unalloyed Copper in NaCl Solution: A Comparative Study Between the Micro and Macro Scales

Abstract

The effects of pH and chloride concentration on the electrochemical corrosion of copper in aqueous sodium chloride (NaCl) media were studied at the micro scale using a microcapillary droplet cell and at the macro scale using a conventional large scale cell. Using an experimental design strategy, electrochemical response surface models of copper versus pH and NaCl concentration were constructed with the minimum number of experiments required. Results show that the electrochemical behavior of copper under corrosive media shows significant differences between the micro and macro scale experiments. At the micro scale, the pit initiation of copper occurs at more negative potentials for high NaCl concentrations and alkaline pH values. Also, the micro scale potentiostatic measurements indicate higher stabilised passive currents at high NaCl concentrations and low (acidic) pH values. At the macro scale, the pH is shown to have a greater influence on the corrosion potential. The chloride concentration is the most significant factor in the passive current case while at the micro scale the effect of these two factors on the passive current was found to be the same. The surface morphology of the formed patina on the corroded copper in both micro and macro systems reveal a more significant role of the chloride concentration on the structure and the grain size of the patinas. Finally, micro and macro electrochemical impedance spectroscopy of copper at various NaCl concentrations and pH values demonstrates a different behavior of copper after several potentiodynamic polarization cycles.

Desalination of Water Using ZVI (Fe0)

“…The Eh and pH of the product water ( Figures C1-C17) indicate that the Cu 0 is held outside the passivation range for much of the reaction time, with the dominant precipitated products (in saline water) likely to be CuO and Cu2O [19,[232][233][234]. …”

Inhibition of Brass (80/20) by 5-Mercaptopentyl-3-Amino-1,2,4-Triazole in Neutral Solutions

“…A single peak corresponding to the oxidation of copper to Cu + is observed on the anodic curve of the alloy, while the second peak denoted as oxidation of copper to Cu 2+ , observed for pure copper [29,35,50], is not observed (Figure 2). The polarization curves are close, presented in [19,20,49], despite the media and composition are not identical.…”

“…In our case, adding 0.01 M NaCl notably decreased Zn content in the surface film, leaving the thicknesses of complex and oxide unchanged for the same immersion time. There are some studies devoted to effects of the chloride ions on the behavior of copper and brass [17,22,26,[50][51][52][53][54], and it was shown that only large concentrations substantially influence kinetics of the formation and composition of various films on the surface of metals. In our case, adding 0.01 M NaCl notably decreased Zn content in the surface film, leaving the thicknesses of complex and oxide unchanged for the same immersion time.…”

Corrosion properties of nickel coatings obtained from aqueous and nonaqueous electrolytes

“…Nickel coatings are quite stable in alkaline media but are easily dissolved in most acids, and many ions, for example, chloride or fluoride, cause rapid deterioration of the metal surface. For this reason, chloride‐containing media are widely used to study corrosion processes . Nickel coatings are also used under different conditions, and this requires study of the corrosion behavior of nickel coatings in the most prevalent aggressive environments …”