galvanic corrosion - do I need to worry - JeepForum.com
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post #1 of 18 Old 08-02-2012, 06:57 PM Thread Starter
redsoxski
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galvanic corrosion - do I need to worry

Been hearing about galvanic corrosion but don't really understand it. I am thinking of putting aluminum corner guards on my wrangler LJ. The tub of the Jeep is painted, no bare metal. I'd like to keep the corner guard bare aluminum, no paint. So, do I need to worry about galvanic corrosion here in the dry Colorado air? If yes, is there something I can do to prevent it? Thanks...

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post #2 of 18 Old 08-02-2012, 08:21 PM
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Paint the corners with clear coat paint or treat it with Alodine 1001 Clear...

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post #3 of 18 Old 08-03-2012, 06:47 AM
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I would coat the backside for sure. The corrosion is caused by dissimular metals which is as bad or worse than rust.
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post #4 of 18 Old 08-03-2012, 01:17 PM
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Instead of galvanic, perhaps you meant cathodic?
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post #5 of 18 Old 08-05-2012, 07:39 AM Thread Starter
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Galvanic is what I meant although I believe cathodic may be another commonoly used term. I think coating is the way to go, I'll definately coat the back side. What about the SS fasteners, should I put some sort of gasket or rubber washer between those and the aluminum?
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post #6 of 18 Old 08-05-2012, 08:07 AM Thread Starter
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Just looked up Alodine 1001, can't recall reading a MSDS with precautions like this - must be some nasty stuff, don't know if I want to deal with it..

The WARNING LABELS state the following.

POSSIBLE CANCER HAZARD: Contains chromic acid which may cause cancer. Risk of cancer depends on duration and level of exposure.

WARNING: May cause eye burns and skin irritation. Harmful if sqallowed. Contact with organic materials may cause a fire after evaporation of water. Contains acidic chromates and Fluorides.


Avoid contact with eyes, skin and clothing.
Avoid breathing mist from solution.
Avoid contact with combustible materials.

In case of contact flush eyes or skin with plenty of water for at least 15 minutes.

SKIN CONTACT: Immediately take off all contaminated clothing. Flush with large amouints of water. Soak the affected area for one hour in an iced solution of (0.13 %) of Zephiran chloride (30 cc of 17% concentrate per gallon of iced distilled water.)

GET MEDICAL ATTENTION IMMEDIATELY.

Remove contaminated clothing and/or shoes. Wash clothing before reuse.

DISCARD contaminated shoes.

Also comes with six pages of "material Safety Data Sheet."

Lastly. FOR PROFESSIONAL AND INDUSTRIAL USE ONLY.
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post #7 of 18 Old 08-05-2012, 10:09 AM
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Quote:
Originally Posted by redsoxski View Post
Galvanic is what I meant although I believe cathodic may be another commonoly used term. I think coating is the way to go, I'll definately coat the back side. What about the SS fasteners, should I put some sort of gasket or rubber washer between those and the aluminum?
A galvanic electrical reaction occurs when dissimilar metals along with an electrolyte (typically water or a salt) are introduced together. The metal serving as the anode corrodes while the metal serving as the cathode does not.

You don't have to have dissimilar metals for this to happen. You just need an anode, cathode (both of which can be within the same metal), a metallic path connecting the anode and the cathode, and an electrolyte.

Typical protection is to coat the metal preventing any electrolyte and thus breaking the electrical circuit.
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post #8 of 18 Old 08-05-2012, 01:02 PM
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Quote:
Originally Posted by redsoxski
Just looked up Alodine 1001, can't recall reading a MSDS with precautions like this - must be some nasty stuff, don't know if I want to deal with it..

The WARNING LABELS state the following.

POSSIBLE CANCER HAZARD: Contains chromic acid which may cause cancer. Risk of cancer depends on duration and level of exposure.

WARNING: May cause eye burns and skin irritation. Harmful if sqallowed. Contact with organic materials may cause a fire after evaporation of water. Contains acidic chromates and Fluorides.

Avoid contact with eyes, skin and clothing.
Avoid breathing mist from solution.
Avoid contact with combustible materials.

In case of contact flush eyes or skin with plenty of water for at least 15 minutes.

SKIN CONTACT: Immediately take off all contaminated clothing. Flush with large amouints of water. Soak the affected area for one hour in an iced solution of (0.13 %) of Zephiran chloride (30 cc of 17% concentrate per gallon of iced distilled water.)

GET MEDICAL ATTENTION IMMEDIATELY.

Remove contaminated clothing and/or shoes. Wash clothing before reuse.

DISCARD contaminated shoes.

Also comes with six pages of "material Safety Data Sheet."

Lastly. FOR PROFESSIONAL AND INDUSTRIAL USE ONLY.
I use the Alodine 3001 system all the time on aircraft and as long as you wear gloves and coat it outdoors, there's no problems...

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post #9 of 18 Old 08-05-2012, 01:49 PM
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You can buy non-chromate Alodine. It's less of a health risk.
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post #10 of 18 Old 08-11-2012, 04:42 AM
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it will be fine just left raw. particularly if using stainless fasteners. almost everything bolted together made of aluminum is done so with fasteners other then aluminum. i live in a very corrosive environment and rust is much worse then anything aluminum will get regardless of whats touching it. if you are worried about that then id suggest painting your transmission and tcase too.

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post #11 of 18 Old 04-26-2019, 08:11 AM
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Quote:
Originally Posted by Zone View Post
A galvanic electrical reaction occurs when dissimilar metals along with an electrolyte (typically water or a salt) are introduced together. The metal serving as the anode corrodes while the metal serving as the cathode does not.

You don't have to have dissimilar metals for this to happen. You just need an anode, cathode (both of which can be within the same metal), a metallic path connecting the anode and the cathode, and an electrolyte.

Typical protection is to coat the metal preventing any electrolyte and thus breaking the electrical circuit.
What about an Aluminum skid plate attached to steel parts (bumper etc.) ? How do I deal with the bolts?
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post #12 of 18 Old 04-27-2019, 04:22 AM
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Someone please correct me if I'm wrong but this is the route I'd take:

Use some Yellow Zinc (zinc chromate) grade 8 bolts, with some anti-seize. The yellow zinc offers a bit better protection than your standard "clear/blue" zinc (they used to coat B-25 bombers in YZ before painting).

The anti-seize will ensure you're able to remove the fasteners later even if they do start to exhibit signs of corrosion.

Keep in mind most bolts that are sold are going to be coated in some form of zinc for this exact reason. The zinc coating itself acts as the anode, in normal circumstances. Ideally the zinc would completely corrode before any of the underlying steel actually corrodes. In other words there are ways in which people smarter than us have been able to take advantage of this scientific property.
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post #13 of 18 Old 04-27-2019, 08:23 AM
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Quote:
Originally Posted by JohnPouliot View Post
What about an Aluminum skid plate attached to steel parts (bumper etc.) ? How do I deal with the bolts?
As suggested in the previous posting, zinc chromate hardware, and anti-seize.



Snow melting road salt, ocean salt water, and trapped mud corrosion is what everyone needs to actually deal with. A coat of paint between dissimilar metals is all that is necessary, should galvanic corrosion actually be an issue worth worrying about.

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post #14 of 18 Old 04-29-2019, 05:35 AM
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Thank-you
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post #15 of 18 Old 05-09-2019, 09:36 PM
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I'm surprised nobody mentioned any sealer or gaskets to help keep out dirt that can remove coatings and leave a home for rust to start. Wouldn't something like seam sealer help with this problem too?
I ask because after I removed my rocker and corner guards I found that sand had gotten behind and scrubbed the paint away from several places. I was planning to use something like seam sealer to help prevent this and other problems like the OP was worried about. If it's not a good idea, please explain why.
Thanks
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