Influence of corrosion scales on copper corrosion by-product release

Abstract

Based on a literature study and experiments the copper corrosion mechanism is subdivided into three processes: copper oxidation, deposition of corrosion by-products, and establishment of a solubility equilibrium. This approach is applied to explain the results of a study on the influence of temperature on copper dissolution and deposition of copper corrosion by-products. Changes in water quality are monitored by regular sampling, qualitative and quantitative changes of surface layers are studied using computer-supported light microscopy and scanning electron microscopy.

General corrosion of copper in domestic drinking water installations: scientific background and mechanistic understanding

“…62,67 In the absence of cupric ions, the film revealed p type semiconductor properties, which promote the corrosive attack. In a study by Merkel et al, 61 copper concentration during stagnation decreased while malachite surface coverage increased and oxygen consumption (i.e. metal oxidation) did not change.…”

“…However, there is no temperature requirement for performing the test. 81 In a pipe rig temperature study, 36,61 where parallel experiments were performed for the same water at 5, 12 and 18uC, the oxidation of copper was found to be almost independent of temperature (Fig. 6).…”

“…61 It may be concluded that these structures are formed during stagnation. If the formation occurred during flow, preferential growth following the direction of flow should be evident.…”

“…Merkel reports that malachite structures on internal pipe surfaces are almost perfectly round. 61 It may be concluded that these structures are formed during stagnation. If the formation occurred during flow, preferential growth following the direction of flow should be evident.…”

“…In another publication, the changes of the appearance of copper pipe surfaces were reported. 61 In a hard groundwater, the surface coverage of corroded pipes was determined by computer aided light microscopy and quantitative image analysis. 60 At an ambient temperature of ,22uC, malachite formation took place over a period of 100 days until a surface coverage of 80% was reached.…”