Thoughts on Aluminum Panel (Galvanic?) Corrosion Mitigation

[Jebiruph]

(Cross posted on Gladiator forum) https://www.jeepgladiatorforum.com/...vanic-corrosion-mitigation.68354/post-1119797

This post is based on my degree in galvanic corrosion from YouTube university. Please feel free to point out any inconsistencies or inaccuracies.

The latest hinge corrosion TSB includes the use of zinc shims behind the door hinges which indicates that FCA sees this as a galvanic corrosion issue (or at least an issue with a galvanic corrosion fix). For those that don't know, galvanic corrosion results from the direct contact of dissimilar metals. This contact creates an electrical pressure that promotes the loss of electrons into the atmosphere of the less noble metal. Corrosion is the result of the loss of electrons. In the galvanic corrosion world, metals are rated from more noble to less noble, where the more noble metal will cause corrosion in the less noble metal. Since zinc is less noble than aluminum (which is less noble than steel), zinc is used as a sacrificial anode and will corrode (give up it's electrons) in place of aluminum.

Another factor needed for the corrosion to form is the ability for the electrons to be absorbed into the atmosphere. This requires an electrolyte which is typically moisture or. A lack of moisture or water is why metal will corrode less in a dry atmosphere.

So either avoiding contact with dissimilar metals, implementing a sacrificial anode, preventing contact with the atmosphere or any of the above should help mitigate galvanic corrosion. To that end, here's what I've thought of so far.

The zinc shim currently being used by FCA as a sacrificial anode will be great when they are available, but as an alternative how about a zinc washer on the door hinge. Time (or opinions) will determine the effectiveness of this.
Here's what a m10 washer with a 20mm outside diameter looks like on the door nut.

Here's one with black permanent marker around the edge so it doesn't show as much.

All of my door hinge corrosion has started at the pin, which I attribute to that being the connection to the dissimilar metal in the rest of the Jeep and also to damage done to the paint from opening and closing the door. My plan is use these Delrin hinge liners to replace the metal hinge liners to both electrically separate the hinge from the body and to also provide a more paint friendly surface for the hinge to pivot on.

And since access to the atmosphere with the presence of moisture or water is also needed for galvanic corrosion, my thought here is to apply strips of paint protection film around the lower edges of the panels to help isolate these corrosion prone areas from moisture and the atmosphere. No pictures of this yet.

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[dragoneggs]

Galvanic corrosion has been an issue that has been continuously addressed in aerospace for decades… especially when composite (graphite) structural components became mainstream in commercial design. To this day, designs consider coatings and other ways to isolate dissimilar materials that otherwise create a ‘battery’ or one might say ‘energy’ that is wasted and destructive.

Mating aluminum and steel is not a durable solution without multiple barriers in place.

 

[dcmdon]

Or sacrificial anodes.

 

[dcmdon]

Can you all comment on this.

1) I've got concerns about doing this because I'm afraid they are going to bugger up the Torx screws that hold the doors in. It's not hard to imagine getting the jeep back with the paint all chipped up.

2) Do they put the zinc shims go between the door and the hinge? So probably 4x2" or so and probably only a few thousandths thick?

I've removed the cowl bolts to put mirror mounts on and they were TIGHT. I parked the truck facing the sun so the surface got up to 120 deg or so and then used a very high quality, very snug Torx wrench to remove them. No issues. But I can't imagine a tech being paid on flat rate being very careful.

 

[Dyolfknip74]

I personally think it's a combo of shitty paint/prep and some cases of galvanic corrosion. Mainly because the bubbles don't always appear where there are dissimilar metals like at the bottom of the doors.
I yanked my hinges and Linex'd them so they wouldn't get beat to shit from rocks anyway and I haven't run door screws for over 2 years. Didn't run them at all in my JK for 5 years.

 

[Fudster]

I wonder to what extent the application of petroleum jelly on the moving parts might help here not simply as lubricant, but more importantly--given the product's hydrophobic nature--the prevention of water buildup--given water's role here as an electrolyte....

...not unlike people's application of petroleum jelly on removed ***battery terminals prior to their being (re)secured to the battery

(*** battery defined here as that "heavy black box" that sits under a vehicle's hood, as opposed to the unintentional 'battery' and corrosion created when dissimilar nobility metals are connected in the presence of an electrolyte)

 

[TheNewGuy]

Sadly it appears one of my hinges is in the early stages of corrosion. Oct '21 build, 11.5k miles, garage kept, factory hinge bolts removed and replaced with silver bullet hinge pins early on. Doors have been off 3x and handled with kid gloves.
Disheartening....

.

 

[Jebiruph]

Sadly it appears one of my hinges is in the early stages of corrosion. Oct '21 build, 11.5k miles, garage kept, factory hinge bolts removed and replaced with silver bullet hinge pins early on. Doors have been off 3x and handled with kid gloves.
Disheartening....

.

It looks like water gets trapped in the crack under the paint and eventually causes (facilitates) the corrosion. Here's some pics of one of my hinges that shows the corrosion where the paint covers the crack and no corrosion where the crack is open. The first arrow points to where the crack starts getting covered with paint, the second arrow shows no paint and no corrosion in the back.. Boeshield was recommended on the Gladiator thread to seal cracks from moisture.

 

[Jebiruph]

Can you all comment on this.

1) I've got concerns about doing this because I'm afraid they are going to bugger up the Torx screws that hold the doors in. It's not hard to imagine getting the jeep back with the paint all chipped up.

2) Do they put the zinc shims go between the door and the hinge? So probably 4x2" or so and probably only a few thousandths thick?

I've removed the cowl bolts to put mirror mounts on and they were TIGHT. I parked the truck facing the sun so the surface got up to 120 deg or so and then used a very high quality, very snug Torx wrench to remove them. No issues. But I can't imagine a tech being paid on flat rate being very careful.

After my first experience where they damaged and reused the door hinge bolts, I started providing new bolts (a little over $1 each) for them to paint and for me to install later.

 

[TheNewGuy]

It looks like water gets trapped in the crack under the paint and eventually causes (facilitates) the corrosion. Here's some pics of one of my hinges that shows the corrosion where the paint covers the crack and no corrosion where the crack is open. The first arrow points to where the crack starts getting covered with paint, the second arrow shows no paint and no corrosion in the back.. Boeshield was recommended on the Gladiator thread to seal cracks from moisture.

Boeshield is definitely worth a try

 

[Fudster]

Please don't misunderstand my intent. I'm all about methods that prevent the galvanic corrosion that Jerry's raised. But there's this:

I've had to replace a couple of door hinges since purchase for reasons not related to this problem. They're not that pricey, and easy to match with a can of Mopar matching spray paint.

I'd recommend applying the paint lightly in several coats.

 

[TheNewGuy]

It looks like water gets trapped in the crack under the paint and eventually causes (facilitates) the corrosion. Here's some pics of one of my hinges that shows the corrosion where the paint covers the crack and no corrosion where the crack is open. The first arrow points to where the crack starts getting covered with paint, the second arrow shows no paint and no corrosion in the back.. Boeshield was recommended on the Gladiator thread to seal cracks from moisture.

The back of mine doesn't look as open as yours but I'll have to take the door off to get a better look. Maybe some Boeshield and then a coat of touch up paint on the seam will do the trick.

 

[Jebiruph]

The back of mine doesn't look as open as yours but I'll have to take the door off to get a better look. Maybe some Boeshield and then a coat of touch up paint on the seam will do the trick.

I would hesitate to apply more paint as it may exacerbate the problem. I've got some Boeshield on order as a preventative and am also going the see what TurtleWax Graphene Flex does on the flat surfaces to prevent the corrosion. And also see how to remove and repair the existing corrosion.

 

[TheNewGuy]

I would hesitate to apply more paint as it may exacerbate the problem. I've got some Boeshield on order as a preventative and am also going the see what TurtleWax Graphene Flex does on the flat surfaces to prevent the corrosion. And also see how to remove and repair the existing corrosion.

I just figured if the issue is the open seam on the back of the hinge, sealing it with paint like the front of the hinge would prevent moisture from getting in there on the future.

 

[Jebiruph]

I just figured if the issue is the open seam on the back of the hinge, sealing it with paint like the front of the hinge would prevent moisture from getting in there on the future.

Paint doesn't make a good seam sealer and may trap water instead of blocking it. The bubbling of your paint has probably compromised the surface and may also allow water penetration.

My plan is to cut away the corroded paint and clear the seam, treat the underlying corrosion and repaint without painting over the seam. Then I'll use something to moisture seal the seam.

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