Stray Electrical Current Detection

[GordMay]

Originally Posted by Bertinc

Another important consideration when buying Reuther new or replacement anodes is to make sure they are mil. spec. This insures their makeup complies with strict guidelines, meaning not junk metal.
A previous post mentioned Performance Metals as a good resource and I believe I saw Dave Rifkin’s website mentioned, Quality Marine Services. These two sources will give good guidance on marine corrosion; a difficult subject to cover in a blog.

Performance Metals “Navalloy” aluminum anodes are manufactured to the military specification MIL-DTL 24779* and are claimed to be suitable for use in all water types: salt, brackish, or fresh.

* Aluminum Alloy U.S. Military Specification ➥ https://boatzincs.com/pdfs/Mil-Spec%2024779B(SH).pdf

Zinc Alloy U.S. Military Specification: MIL-DTL-18001KL

[Bertinc]

Going back to the original post about corroding underwater metals, I don’t think anyone mentioned the importance of checking the GI (Galvanic Isolator).
This piece of engineering marvel goes between the incoming boats grounding conductor (shore power) and the ground buss, effectively shunting up to -1.2 volts that might’ve found its way to your boat from an offending boat(s).
These devices need to be checked annually to assure they’re working properly. Lightning strikes are the main culprit but also surges can cause failure.
Newer GIs, installed on boats since 2011, fail “closed” for safety, but that leaves the boat vulnerable to corrosion. Older GIs might fail “open” so they dangerously disconnect the the boat’s ground from shore.
To check use a multimeter with a diode check function.
Google “how to test a Galvanic Isoltor” for more information.

[LargeMarge]

re -- hull cleaners in Frisco Bay
.
During the video, they discuss the conductivity of fresh water vs salt water.
Apparently, fresh water transmits electricity less efficiently, then as the electricity encounters the salinity of a human, the pulse is amplified.
Or something.
.
In salt water, the electricity continues around a human without such a dramatic stop.
Or something.
.
In your environment, I think the Delta brackish (and river water...) could present a substantial potential the further from the Gate and the Pacific.

[NormanMartin]

I have used a silver/silver-chloride half cell to manage cathodic corrosion. Simple and inexpensive.
Look up www.boatzincs.com

[fstbttms]

Originally Posted by LargeMarge

re -- hull cleaners in Frisco Bay
.
During the video, they discuss the conductivity of fresh water vs salt water.
Apparently, fresh water transmits electricity less efficiently, then as the electricity encounters the salinity of a human, the pulse is amplified.
Or something.
.
In salt water, the electricity continues around a human without such a dramatic stop.
Or something.
.
In your environment, I think the Delta brackish (and river water...) could present a substantial potential the further from the Gate and the Pacific.

Let me clarify a few things for you:

1.- Humans are essentially bags of saltwater. When surrounded by saltwater, humans do not have a large difference in potential and therefore are unlikely to attract electricity. When surrounded by freshwater, humans do have a large difference in potential and are much more likely to attract electrical current. It is for this reason that ESD is largely unheard of in saltwater marinas.

2.- Relatively little in-water hull cleaning occurs in the Delta or rivers

3.- Frisco is a place in Texas.

[goboatingnow]

Originally Posted by Bertinc

Going back to the original post about corroding underwater metals, I don’t think anyone mentioned the importance of checking the GI (Galvanic Isolator).

This piece of engineering marvel goes between the incoming boats grounding conductor (shore power) and the ground buss, effectively shunting up to -1.2 volts that might’ve found its way to your boat from an offending boat(s).

These devices need to be checked annually to assure they’re working properly. Lightning strikes are the main culprit but also surges can cause failure.

Newer GIs, installed on boats since 2011, fail “closed” for safety, but that leaves the boat vulnerable to corrosion. Older GIs might fail “open” so they dangerously disconnect the the boat’s ground from shore.

To check use a multimeter with a diode check function.

Google “how to test a Galvanic Isoltor” for more information.

I’m happy enough to place my trust in the onboard RCBO to trip even if the PE connection is severed.

[GordMay]

Design and testing requirements for RCBOs are outlined in the set of standards: IEC/EN 61009: Residual current circuit-breakers with integral overload protection for household and similar uses [RCBO].
RCBOs] should operate within 25-40 milliseconds of the detection of leakage currents (through a person) in excess of 30mA. However, it is also important to note that this is only true for final circuits less than 32Amps.

A current as low as 0.25 milliamperes [mA], entering the body, can cause a buzzing or tingling sensation, that doesn’t cause injury.
When a current above 10 mA travels through flexor muscles, such as the ones in our forearms, that close the fingers, it causes a sustained contraction. The victim may be unable to let go of the source of the current, making the duration of the contact longer, and increasing the severity of the shock. If you can’t let go, current continues through your body for a longer time, which can lead to respiratory paralysis (the muscles that control breathing cannot move). The let-go threshold is the level where a person’s muscles contract, meaning that they are unable to let go of the electrical source until someone safely removes it. You stop breathing for a period of time. People have stopped breathing when shocked with currents from voltages as low as 49 volts. Usually, it takes about 30 mA of current to cause respiratory paralysis.
When a current above 10 mA travels through extensor muscles, it causes a violent spasm. If the muscles affected are the hip extensors, that lengthen the limbs away from the body, the victim may be propelled, sometimes many metres away!
If a current of 50 mA passes through the heart, it can cause cardiac arrest [ventricular fibrillation].
When a current above 100 mA passes through the body, it leaves marks [electrical burns] at the points of contact with the skin.

More ➥ https://www.ebmedicine.net/topics/bu...ic-shock-burns

[Bertinc]

Originally Posted by Moonshine36

So I have read about the damage to boats underwater metals caused by stray electrical current. Most of what I've read talks about electrical shock drowning mostly in fresh water. My concern is not so much about drowning as I am located in the PNW in a cold salt water environment which not really suitable for swimming....
My question: Is there a simple way that I can check the waters around my boat to see if my boat or one of my neighboring boats in the marina are leaking stray electrical current into the water ?

To reiterate: it’s 12 volt DC leakage voltage that affects underwater metals and 120 volt AC leakage that causes Electric Shock Drowning.
These are two separate conditions and yes both are measurable as was previously discussed on this forum.
There’s a lot of information in the internet but be careful that it comes from a reliable source. The ABYC is a reliable source along with Capt. David Rifkin, Performance Metals, Kevin Ritz (Electric Shock Drowning.Org)

Terminology is important in talking about simple corrosion, galvanic corrosion, and electrolytic corrosion as correct terms. Electrolysis is a hair removal process and also a process by which electric current is passed through a substance to effect a chemical change where the substance loses or gains an electron.
So you can see, the term electrolysis is a commercial manufacturing term and not what happens to metals in our boats. If there’s any talk about electrolysis it doesn’t have anything to do with boats and that person is not to be deemed a credible information source.
Thanks and I’ll get off my soap box now.

[fstbttms]

Originally Posted by Bertinc

Terminology is important...

[CharlieJ]

@Bertinc #53:

[Bertinc]

Just read a post about electricity in by salt/fresh water that maybe I can offer another explanation.
In general, for current to flow you need a voltage difference called voltage potential.
In the case of Electric Shock Drowning in fresh water a human body with it’s make up of sodium becomes a better conductor than the surrounding fresh water.

In fresh water, stray current emanating from a fault through a boat’s propeller or even a plugged in shore power cord dropped in the water creates voltage gradients similar to the analogy of dropping a stone in the water creating ripples. When a human body comes in contact with a voltage gradient, stray current flows and it only takes approximately 1.5 volts per foot of contact to initiate muscular paralysis. Sure there’s variables like what clothes or insulated material is worn but dangerous currents can readily flow across a swimming horizontal body. In the event of swimming and feeling a tingling sensation the recommendation is to go vertical, reducing your exposure to the voltage gradients, thus current , and back peddle out.

Salt water is a good conductor acting to open the circuit; trip the circuit breaker or blow the fuse. That’s why there’s no documented cases of ESD in salt water.
The caveat is that when there is rain flooding or storms,
fresh water tends to sit on top of the denser salt water before diluting so be aware of your environment.

Another basic fact of electrical circuits; the current is always trying to get back to it’s source. In normal operation the current goes out on one insulated wire to the load and returns on the other insulated wire. When one wire inadvertently comes in contact with a conductive surface or human body, depending on resistance and voltage gradients, current flows through any and all paths trying to get to its’ source. Hence the important reason for the grounding (green) conductor. This is termed a ground fault as our electrical system is based on the grounded system.
Now when you install an isolation transformer rules change and are too complicated to explain accurately here.

Last point in checking for AC leakage current by clamping an ammeter around a shore power cord is to be aware of cycling loads that when off may give an erroneous reading. Battery chargers, inverters, water heaters and water cooled a/c condensers all cycle on and off.