Talk:Cold water pitting of copper tube

Comment
The article quotes "The corrosion rate of copper in most potable waters is less than 25 µm/year, at this rate a 15 mm tube with a wall thickness of 0.7 mm would last for about 280 years.[1]". Looks like there is a silly mistake somewhere. 0.7mm is 700µm. 700/25=28 years. The actual corrosion rate for total erosion in 280 years would be 2.5µm/year. Given copper pipes need structural integrity (for compression joints, and external in-use forces) and to resist internal water pressure, and given corrosion rates and thicknesses across an individual tube vary slightly, there will be a minimum thickness where failure becomes likely, or inevitable. Perhaps 0.4mm. This would give a maximum safe internal erosion of perhaps 300µm before a pipe is rendered unserviceable. Assuming the copper doesn't embrittle, with 2.5µm/year as a lower limit of erosion would give an upper limit of service life of 120 years. I have replaced 15mm copper in busy straight-run freshwater supply pipe, in a hard water area, failed due to erosion in 10 to 15 years.Nick Hill (talk) 13:23, 9 March 2012 (UTC)

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