| Summary: | In order to investigate the role of chloride ion in the corrosion film formation of copper and its evolution over time, the initial corrosion behavior of copper in neutral 3.5% (wt.) NaCl solution was characterized by in-situ Raman spectroscopy along with electrochemical tests. The results demonstrated that the cuprous chloride complexes, such as CuCl and <inline-formula> <math display="inline"> <semantics> <mrow> <msubsup> <mrow> <mi>CuCl</mi> </mrow> <mn>2</mn> <mo>−</mo> </msubsup> </mrow> </semantics> </math> </inline-formula> were produced through electrode processes, while the cuprite, <inline-formula> <math display="inline"> <semantics> <mrow> <msub> <mrow> <mi>Cu</mi> </mrow> <mn>2</mn> </msub> <mi mathvariant="normal">O</mi> </mrow> </semantics> </math> </inline-formula> seemed to be formed via the chemical precipitation reaction instead of a direct electrochemical transformation from the metal matrix or CuCl and it occurred rather slowly. At the open circuit potential, the chlorides were generated first in the initial 2 h and then they transformed to the oxides with the <inline-formula> <math display="inline"> <semantics> <mrow> <msubsup> <mrow> <mi>CuCl</mi> </mrow> <mn>2</mn> <mo>−</mo> </msubsup> </mrow> </semantics> </math> </inline-formula> content in the interface increasing. The in-situ Raman characterization directly evidenced the previously reported mechanism of growth of oxide layers on copper surfaces in neutral <inline-formula> <math display="inline"> <semantics> <mrow> <msup> <mrow> <mi>Cl</mi> </mrow> <mo>−</mo> </msup> </mrow> </semantics> </math> </inline-formula> media and clearly showed the formation of a corrosion product film and its evolution over time. The electrochemical tests corresponded to the results of in-situ Raman characterization well.
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