Are stray currents a danger for plants with metal tubes?

Stray currents (also known as Eddy currents or, incorrectly, as galvanic currents) are currents that stray from their “normal” route, that is, the primary circuit, represented by normal electric conductors, to then disperse in the ground and penetrate other metal structures, known as secondary conductors.

After travelling along a stretch of metal tubing, these currents leak again and corrosion occurs. It should be pointed out that stray currents can only cause damage if these currents are direct currents. On this point, it is worth noting how the current found in our homes is not direct but alternate. We should also point out that cement mortar offers a considerable level of electric resistance. Subsequently, by carefully analysing the case of copper tubes, it is clear that there are numerous factors which drastically limit corrosion phenomena of this kind from occuring: stray current corrosion in a home, including the laying below ground, is, therefore, an extremely rare occurrence. It might be worthwhile noting how the cases of corrosion incorrectly attributed to stray currents, almost always relate to tubes carrying cold water and never those transporting heating or gas. If the cause were really due to stray currents, we would need to imagine that these currents are so “intelligent” that they select the tube they wish to attack according to its use. Clearly, this is not the case, so the cause of corrosion must be attributed to other aspects. Further confirmation of the doubts regarding the real plausibility of stray currents can be found in SCTubes history where there are no cases of corrosion resulting from stray currents in copper tubing in systems found in homes.

In reality, in the 1970s, there was a case of corrosion on external tubing in a building but it occured during construction caused by stray currents from a welding iron that was not properly attached to the structure it was welding.

The cause, in the few cases of corrosion (a few, especially if we consider the tens of millions of metres of copper tubes installed annually) needs to be sought out elsewhere, for example in an excessive amount of carbon deposits on the internal surface of the tube; so, the first preventative measure (and one of common sense) is to purchase high quality tubes with a low level of carbon residue.

On this subject, we should remember that the SCUDO® copper tube is manufactured using a production process of internal pre-passivation which combats the contents of carbon residue by more than 70% compared to that specified in the EN 1057. Summing up, experience shows how the corrosion for stray currents in a building is limited to exceptionally rare episodes and is certainly not a determining factor when selecting the material. The supposed danger of this phenomenon is frequently demonised but the argument, in most cases, is exploited for reasons less dignified than one of prevention.