[quote=spdrun]I wasn’t speaking to dissimilar metal corrosion, only to corrosion due to the pipes being used as ground. It shouldn’t be significant since current flowing through ground is normally zero (and A.C., not D.C. if there is one).[/quote]Under normal conditions that is true. Interesting factoid is that under strain/earthquake conditions.. quartz can generate significant voltages.
BTW, My response with respect to galvanic action was due to this statement:
[quote=spdrun]
I think that when the pipes became copper, things change. You can cause current based copper erosion from galvanic action.
Practically, it should be a non-issue since ground shouldn’t have (significant) current flowing through it under normal operating conditions. Yeah, I know some timers and things like that can use it as a return path, but it’s rare.[/quote]
It is an issue because copper vs. cast-iron or steel forms a battery. Most mains are cast iron or galvanized steel. Newer houses are copper. Newer water main replacement pieces may be PVC(green). Wet or damp soil forms free ions from different types of ‘salts’ (Salts can be things like copper-chloride, not just sodium-chloride). These ions complete the circuit for the ‘dissimilar metal’ battery. Because the dissimilar metals form a battery, they also form the needed current (Current is actually the result of their corrosion). They just need an ion path for the return current. Water that is not pure/distilled water can also complete an electrical circuit. Purity in water can be measured in some extent, but the water’s willingness to carry electricity. If it will not carry electricity, it is pure – ion free. There is also research and experimentation on ships in salt water using voltage generators to oppose the current produced by corroding steel, and thereby stop shipboard corrosion.
[quote=spdrun]
OTOH, using piping as neutral return would probably yield amusing results.[/quote]
If you saw the posts between myself and Blogstar, piping was once used as neutral/ground on old AC systems(Alternating Current that is, not Air Conditioning). Don’t really need a return for AC, just a large capacitance sink. These old systems were all galvanized steel/cast iron, no copper. They used the mains as part of the ground-plane.
[quote=spdrun]BTW – I’ve seen the videos of people being hooked up to work on H.T. lines from a helicopter — that takes some serious cojones! Thanks for mentioning that again. And you’re basically right about everything electrical you’ve posted here — are you an EE?[/quote]Yep. EECE/UCSD/Revelle oldtimer. I put myself through college building houses.
