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Research into the mechanism of pitting corrosion has been undertaken by the copper industry in many countries of the world. Pitting occurs typically in cold, aerated, hard, organically pure waters from deep wells or boreholes and not in surface waters as generally used.
Borehole water and surface water can vary widely throughout the different areas of South Africa. The only regulations relating to potable water at present are those of the SABS which are classified as guidelines/recommendations and cover the health aspect rather than a corristivity with relation to any type of tubing used for reticulation of the water. Not all borehole waters are corrosive to copper or other types of available tubing, but a good general rule would be to have the water tested before selecting the type of tube to be used to ensure maximum durability of the installation.
Concrete & Chasing
Considerable research has been conducted on the effect of concrete on the corrosion of copper tubes and to quote from an International Copper development Council report: technical report Number 201 "copper tubes in ordinary Portland cement or concrete made with it do not suffer corrosive attack, but from an uniform adherent oxide layer. Similarly concrete with calcium chloride added has no corrosive effect even when the set concrete is kept intermittently or permanently wet.
An element often overlooked when considering the coupling of dissimilar metals is carbon. Practically all metals when coupled to carbon under the correct conditions would become anodic.
It would therefore be advisable to guard against the use of copper with ash bricks or cinders when used as backfill or the contamination of sand or concrete mix with ash from on-site open fires.
Under these conditions, with a strong electrolyte present, active galvanic cells could be set up and localised corrosion of the copper tube could take place resulting eventually in failure.