Author Topic: Vehicular Electronic Anti-Corrosion systems ... candidate for debunking?  (Read 7989 times)

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Offline ornea

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Some people swear by these devices that claim to inhibit corrosion on vehicles, but I smell bs. 

There is a big list of disclaimers ... unsuitable for old paint, old cars, bare metal. Basically only good for situations where rust is unlikely.

Perhaps a debunking candidate.

 

Offline rs20

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I haven't even looked at this yet (in the few seconds I have spare I couldn't even find a way to see the text of the patent), but here's a patent to dissect: http://pericles.ipaustralia.gov.au/ols/auspat/applicationDetails.do?applicationNo=2007236536
 

Offline Fungus

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Some people swear by these devices that claim to inhibit corrosion on vehicles, but I smell bs. 

There is a big list of disclaimers ... unsuitable for old paint, old cars, bare metal. Basically only good for situations where rust is unlikely.

Perhaps a debunking candidate.
'Cathodic Protection' is well known and widely used. It works.

https://en.wikipedia.org/wiki/Cathodic_protection

Do those cheesy car-protection devices work, too? That will depend on the device.
 

Offline helius

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There was a thread here on this very subject only a month ago.
https://www.eevblog.com/forum/beginners/anti-corrosion-car-module-bs-or-not/

Do such devices do anything at all? Based on descriptions of their parts, they appear to be useless.
 

Offline aargee

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Catholic protection only seems to work effectively under water, where there is a uniform connection to the protected device by virtue of the water.
Air based electronic rust protection has problems due to the unpredictable or non-existent circuit connectivity through the the atmosphere. Essentially a box with a 555 flashing a LED works just as well.
Not easy, not hard, just need to be incentivised.
 

Offline Fungus

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The way I figure it, we can apply Occam's razor:

If these things actually worked then the manufacturers would build them into the cars. It would be a major selling point for very little extra cost (and they could probably eliminate several rustproofing steps from their process).

The built-in ones would be an order of magnitude more effective then the aftermarket ones because they're engineers and they know what they were doing. They'd know where to place the sacrificial parts, etc.

The manufacturers aren't doing this so therefore they're worthless.

QED.

 

Offline EEVblog

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Offline Fungus

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Catholic protection only seems to work effectively under water, where there is a uniform connection to the protected device by virtue of the water.
Right.

Air based electronic rust protection has problems due to the unpredictable or non-existent circuit connectivity through the the atmosphere. Essentially a box with a 555 flashing a LED works just as well.
They don't actually need to work in the dry, only when your car's wet.
 

Offline nitro2k01

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Catholic protection only seems to work effectively under water
In particular, holy water?  :-DD
Whoa! How the hell did Dave know that Bob is my uncle? Amazing!
 

Offline McBryce

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There was a thread here on this very subject only a month ago.
https://www.eevblog.com/forum/beginners/anti-corrosion-car-module-bs-or-not/

Do such devices do anything at all? Based on descriptions of their parts, they appear to be useless.

I just reverse engineered the PCB from the photos in that thread. You can see what it does(n't) in my schematic: https://www.eevblog.com/forum/beginners/anti-corrosion-car-module-bs-or-not/msg713443/#msg713443

McBryce.
 

Offline German_EE

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Cathodic protection on BOATS works just fine, one or more large lumps of zinc electrically connected to the hull on one side and the salt water on the other. The zinc corrodes instead of the hull as it is a more active metal and no electrical supply is required.

The modules that are for sale for use on cars are bullshit, but I am willing to be proved wrong. The currents running through the chassis as a return from the wiring loom will be greater than the module can supply.
Should you find yourself in a chronically leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks.

Warren Buffett
 

Offline Fungus

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The modules that are for sale for use on cars are bullshit, but I am willing to be proved wrong. The currents running through the chassis as a return from the wiring loom will be greater than the module can supply.
a) Water isn't a very good conductor so maybe current isn't a problem.

b) Do they have to be 100% effective? Reducing rust by a percentage is still worthwhile if they're cheap enough.

« Last Edit: July 20, 2015, 02:48:29 pm by Fungus »
 

Offline helius

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a) Water isn't a very good conductor so maybe current isn't a problem.
I have mainly seen sacrificial anodes used on ocean yachts. The conductivity of sea water is very high, for a small sailboat the resistance between the anode and any other fixture would be less than an ohm. These zinc anodes are used when the craft is at rest; when under power or under sail they are taken out.
Cars already have a form of electrochemical protection in their underpaint coating. The steel parts are pickled and coated in zinc to provide a sacrificial layer that delays rust formation. This layer works because it covers the entire body; if a sacrificial anode is only located in one spot, it would protect that spot, but not anything else that was too far away to complete the circuit.
 

Offline BennVenn

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I helped a mate install HID lights in his new mirage and noticed a little box on the firewall blinking away. It had 3 wires coming out of it, two running directly to the battery and the thrid being eartherd on the opposite side of the engine bay. He said it was part of the 'paint protection package' they sold him, electronic rust protection.

He let me pop the top off to see what was inside. A 555 blinking once every few seconds and a voltage trippler - diode, capacitor, diode, capacitor etc... It was intersting. I flipped the board and both earth wires were soldered to the same point. The output of the trippler was left floating. Do you think the dealer is aware its all a load of crap?

We use zinc anodes in a lot of our gear at work as it is all cooled via seawater. We replace the anodes every two weeks, more often in warmer waters. They do work but they need to be constantly in contact with seawater. We're told they shouldn't be used where copper pipe is used as the zinc plates itself to the copper and nasty things happen.
 

Offline apis

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For catholic protection there need to be a sacrificial anode and a connection through the water so you get a circuit. I don't see how that could be the case in a car? And do they even supply anodes with this device? There must be some other kind of magic for this to work.
 

Offline mtdoc

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For catholic protection ....

Yes, for god's sake. Protect yourself and your vehicle from those Catholics..... :P
 

Offline apis

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Yes, for god's sake. Protect yourself and your vehicle from those Catholics..... :P
It's through the sacrifice of the anode that you protect the Catholics. I think :-\ Not sure how to protect something from the Catholics? Maybe if you turn the anode upside down? ;)
« Last Edit: July 20, 2015, 11:28:06 pm by apis »
 

Offline McBryce

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Don't they just slap a fish sticker on the back of the car to protect themselves?

McBryce.
 

Online gmb42

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To paraphrase a well known movie line:

That ain't cathodic protection, THIS is cathodic protection:



The offshore oil industry and marine engineers have been doing this a long time in a very sophisticated manner.  However their structures are all under the (salty) sea and thus in a conducting medium.  The sacrificial anodes in the image do dissolve remarkably quickly.
 

Online Ian.M

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Has anyone ever heard of such an electronic anti-corrosion system fitted to the above-ground portion of a bridge or other large steel structure?  If the concept actually worked, it would be standard practice on all steel structures and it would be difficult to get insurance for the structure without it.
 

Offline SeanB

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Even oil pipelines use sacrificial zinc or magnesium anodes, along with a thick layer of bitumen applied to all exposed metal and with a geotextile layer wrapped around it and a further 2 coats of bitumen. Old electrical cables used a protective layer of waxed paper, wrapped with cotton, then overwrapped with lead and then 2 bitumenised steel tapes and a further bitumen layer and rubber cover. That lasts around a century.

There are some pipelines with active protection, but that is more a monitoring system to detect when the regular anodes are failed and need replacing, as it is more a monitor of electropotential using carbon electrodes in the ground.
 


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