Electrolytic corrosion around pushpit/foredeck

[Ric]

After two recent boisterous night-passages, where I have had plenty of water coming over the foredeck, I have noticed a great deal of electrolytic corrosion on the foredeck - i.e. iron rust stains leached from the stainless steel pulpit, and oxidising of the aluminium toe-rail. Presumably this is current leakage from the Hellamarine navlights on the foredeck? Any suggestions where the leak might be coming from?

This has coincided with switching to LEDs in the navlights - just coincidence? Or is their a link?

 

[VicS]

After two recent boisterous night-passages, where I have had plenty of water coming over the foredeck, I have noticed a great deal of electrolytic corrosion on the foredeck - i.e. iron rust stains leached from the stainless steel pulpit, and oxidising of the aluminium toe-rail. Presumably this is current leakage from the Hellamarine navlights on the foredeck? Any suggestions where the leak might be coming from?

This has coincided with switching to LEDs in the navlights - just coincidence? Or is their a link?

Id be looking at the electrical connections in the lights and the wiring to them. I be looking for a "short" from the positive to the pulpit.

I'd also check for a voltage reading between the rail and the toe rail ...... even try a small bulb across them if there is a significant reading on a meter.

 

[William_H]

I agree with Vic if it is indeed an electrical induced corrosion then there must be a connection of one of the lamp wires to the base and rail. Something must have changed when you changed the lamps. I would still find it surprising if the lamps caused the problem especially after only 2 nights. Clean up the mess and see what happens in future. good luck olewill

 

[Ric]

That mess was after just one night - I had already cleaned it up after the first occurrence!

Having poked around with a digital multimeter this morning, there does appear to be a voltage differential between the pulpit and the toe-rail of about 130mv with the Nav lights on. I say "appears" because there is a fair bit of fluctuation, depending where I touch the voltmeter probes, and am working alone on a rolly and drizzly anchorage so not easy to be sure.

Interestingly, if I put the old incandescent bulbs back in, the difference is about 40mv, though again this could be measurement error.

I have cleaned up, and I'll do the next night passage with the incandescent bulbs and see if the corrosion occurs again.

 

[vyv_cox]

Difficult to believe that the amount of rust present has come from electrolytic corrosion at such a low voltage in such a short time. Are you sure it isn't the result of some ferrous metal somewhere, or even your anchor chain?

 

[VicS]

Pretty much agree with Vyv

A digital voltmeter has such a high impedance that you can often get readings where an old fashioned moving coil meter would not register any thing

However I'd still investigate the possibility of electrolysis due to a fault (short) between one of the lights, or the wiring, and the pulpit.

I can't believe that much "mess" in a few hours can be due to anything else.