Using a Sacrificial anode on a car to suppress or at least help prevent rusting

On Tue, 12 Apr 2016 09:50:23 -0400, Bob Engelhardt


I assume it's an intermittant thing: when the area is wet, you have an electrolyte. When it's dry, you don't have to worry about corrosion, anyway.
Again, I haven't seen it used on a car. I'm guessing about how it would work in practice.
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Ed Huntress

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On 4/12/2016 10:26 AM, Ed Huntress wrote:

Kinda' - when the _anode_ is wet you get protection, when it's dry and anywhere else is wet, that anywhere else is not protected.

Me too - and my BS detector gave a low-level hum on the OP. The OP had more details than the usual BS, but there is still the fundamental chemistry issue. Maybe the Rolls in the OP had some kind of permanent electrolyte that didn't need to be wetted. But then the anodes wouldn't last 80+ years. I dunno.
Bob
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On Tue, 12 Apr 2016 10:56:59 -0400, Bob Engelhardt

I think I'd have to see it. I can't picture it being very effective, but then, Rolls Royce would go to extremes in the old days, to make everything as perfect as they knew how. Maybe...
I wonder, too, about stray currents. Those are the really big problems with boats, which are docked around electrical currents. The ground rods for shore power -- often just an EMT shield -- tend to eat the submerged metal parts of boats, even when they're protected with sacrificial anodes. You probably have such stray currents in an old car, which tend to have a lot of high-resistance paths to the battery ground.
I'm skeptical but it's not something I've heard about before.
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On Tue, 12 Apr 2016 10:56:59 -0400, Bob Engelhardt

If you place different metals in contact with no electrolyte there is no corrosion. If you place different metals in contact with an electrolyte there is corrosion and if you add an anode the corrosion takes place at the anode.
As has been mentioned they are commonly used on boats and outboard engines and in saltwater cooled marine engines and even large stationary power plants engines usually have anodes.
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On Tue, 12 Apr 2016 10:26:56 -0400, Ed Huntress

The part that is going to rust can be wet and salty while the anode location is clean and dry.
It's been tried - the results are not encouraging - not worth the cost and effort of installing, generally speeking.
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On Tuesday, April 12, 2016 at 7:27:06 AM UTC-7, Ed Huntress wrote:

It works fine; galvanized body was a feature of Americn Motors cars, at least the 1964 Rambler I used to own.
It's not as cheap as good paint, though.
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wrote:

Well, galvanizing is a different story. Any spot that has to be protected is immediately adjacent to zinc in that case.
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On Tue, 12 Apr 2016 09:18:09 -0400, Ed Huntress

It'll work fine on your car if you park it in a full drainage ditch. Doesn't (apparently) work too well dry.
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On Tue, 12 Apr 2016 12:02:38 -0400, snipped-for-privacy@snyder.on.ca wrote:

Yeah, well, cars do get wet sometimes. And when I lived in Michigan, the wet was salt water all winter long.
'Dunno. It's an interesting idea. But having worked on some large boats, and having placed as many as six anodes on a hull to keep the current paths through the water within protected range, I have a hard time imagining how it would work on a car. But then, I haven't seen it or done it.
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On Tuesday, April 12, 2016 at 12:07:05 PM UTC-4, Ed Huntress wrote:
>>

I imagine you could get a bunch of magnesium fire starters like Harbor Frei ght sells and cut each one into three pieces , put a hole thru each piece a nd attach with self tapping screws. Then you could have one mounted close t o every part of the car. But it would be a lot less work to paint places t hat need protection.
Dan
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On Wed, 13 Apr 2016 11:56:49 -0700 (PDT), " snipped-for-privacy@krl.org"

Having restored and repaired a few boat trailers that were regularly dunked in salt water, the best thing I ever tried was a zinc-loaded epoxy coating.
It was miserable to apply (very thick, and it drooled -- not thixotropic at all), and very expensive, but it worked great. I rotated the trailer 90 deg. after painting the top and bottom horizontal surfaces, and then coated tops and bottoms of *those* sides. You have to do that before the epoxy cures but after it starts to gel, or the amine will blush and the overlap won't seal it. Then wash off the amine with soap and water, rough it with steel wool, and coat with a good boat enamel.
Second best was two coats of zinc chromate primer, and then two coats of brush-on Rust-Oleum. That was the fish-oil based stuff that took a week to dry hard.
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Ed

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For this to work there must be an electron pathway between the anode and th e metal to be protected (e.g., a wire or direct contact) and an ion pathway between both the oxidizing agent (e.g., water or moist soil) and the anode , and the oxidizing agent and the metal to be protected, thus forming a clo sed circuit; therefore simply bolting a piece of active metal such as zinc to a less active metal, such as mild steel, in air (a poor conductor and th erefore no closed circuit) will not furnish any protection.
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On Thursday, December 1, 2016 at 9:43:07 AM UTC-5, snipped-for-privacy@gmail.com wrote :

the metal to be protected (e.g., a wire or direct contact) and an ion pathw ay between both the oxidizing agent (e.g., water or moist soil) and the ano de, and the oxidizing agent and the metal to be protected, thus forming a c losed circuit; therefore simply bolting a piece of active metal such as zin c to a less active metal, such as mild steel, in air (a poor conductor and therefore no closed circuit) will not furnish any protection.
First, the issue is protection in a wet environment, so there is an "ion pa thway" (electrolyte). Plain, pure water is not much of an electrolyte -- bu t neither is it a severe corrosion problem. Salt in the water, or even many contaminants, produce more of a corrosion problem AND a better ion pathway .
The direct contact with the metal surface being protected usually is enough of a conducting path. Many protective electrodes used in marine environmen ts are just screwed onto the metal being protected, and they work quite wel l.
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wrote:

First, the issue is protection in a wet environment, so there is an "ion pathway" (electrolyte). Plain, pure water is not much of an electrolyte -- but neither is it a severe corrosion problem. Salt in the water, or even many contaminants, produce more of a corrosion problem AND a better ion pathway.
The direct contact with the metal surface being protected usually is enough of a conducting path. Many protective electrodes used in marine environments are just screwed onto the metal being protected, and they work quite well.
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Ed Huntress

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Conductive drag strap. Martin
On 12/1/2016 9:19 AM, Jim Wilkins wrote:

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Wonder if the anti-static strips that are drug behind cars that work in the gas fields and other explosive places would work as the cathode to 'earth' connection ?
Martin
On 12/1/2016 8:43 AM, snipped-for-privacy@gmail.com wrote:

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On Thu, 1 Dec 2016 06:43:03 -0800 (PST), snipped-for-privacy@gmail.com wrote:

There are ALL KINDS OF ELECTRONIC RUST BUSTERS ON THE MARKET - SOME USING SACRIFICIAL ANODES, SOME NOT - AND none OF THEM TERRIBLY EFFECTIVE AT REDUCING OR PREVENTING RUST.
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On Tuesday, February 27, 2007 at 2:22:46 AM UTC-5, Brent wrote:

Not Nuts... My '02 sebring had magnesium strut cups that corroded and needed replacement in '14 and no rust . Replaced with aftermarket steel and rust started showing finally last winter after 16 years in new england.
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