Dissolution of copper and copper-nickel alloys in aerated dilute HCl solutions

Autor: A.M. Shams El Din, A.M. Taj El Din, M.E El Dahshan
Rok vydání: 2000
Předmět:
Zdroj: Desalination. 130:89-97
ISSN: 0011-9164
DOI: 10.1016/s0011-9164(00)00077-1
Popis: The dissolution of pure Cu, 90 10 and 70 30 CuNi alloys and of Monel 400 in strongly aerated 0.1 m HCl is studied by the weight loss technique at 25°C and 60°C. All four materials behave in a similar manner. The weight-loss/time curves are formed by an initial, low rate, induction period representing the dissolution of Cu in the monovalent state, CuCl2−. The nickel of the alloys dissolves simultaneously, but in quantities higher than present in the solid metal. Air oxidizes Cu+ to Cu2+. When enough of Cu2+ accumulates in solution, the dissolution of Cu is auto-catalyzed through the reaction Cu+Cu2+=2Cu+. This conclusion is supported by the results of experiments in which extra Cu2+ ions are added to the solution. The rate of dissolution along the induction period increases and the period itself decreases and disappears as more Cu2+ ions are added to the acid. A rise in temperature accelerates the dissolution reaction both along the induction as well as the catalyzed stages. The activation energies of dissolution are material dependent and vary between 3 and 11 K cal/mole. The corrosion rate (CR) of the four materials along the induction period varies with the [Cu2+] of the solution according to CR = A[Cu2+]n where A and n are constants. The value of n depends on the Cu content of the alloy. The corrosion rates along the catalyzed reaction are independent of the [Cu2+].
Databáze: OpenAIRE
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