Thoughts on Aluminum Panel (Galvanic?) Corrosion Mitigation

[Jebiruph]

I finally got around to cutting into the blistered paint on the two corroded hinges I'm working with. The paint is tougher than I expected, hard to cut even with a new blade.

I was hoping to find more definitive evidence that the corrosion is originating from the seam between the steel pin flange and the aluminum hinge body, but the evidence wasn't as conclusive as I hoped. The next step is to treat the corrosion and repaint.

Here are some before and after pics to illustrate how much more corrosion there is under the surface than is apparent on the surface.

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[TheNewGuy]

I finally got around to cutting into the blistered paint on the two corroded hinges I'm working with. The paint is tougher than I expected, hard to cut even with a new blade.

I was hoping to find more definitive evidence that the corrosion is originating from the seam between the steel pin flange and the aluminum hinge body, but the evidence wasn't as conclusive as I hoped. The next step is to treat the corrosion and repaint.

Here are some before and after pics to illustrate how much more corrosion there is under the surface than is apparent on the surface.

I'm torn between going this route and risking voiding the corrosion warranty and just letting it go and getting it repaired under the warranty in a few years

 

[bcupton]

I didn't realize this issue could be covered by the corrosion warranty. Unfortunately! My warranty expires 29 July 2023 and NO CJDR can get me in for MONTHS.

 

[Jebiruph]

I'm torn between going this route and risking voiding the corrosion warranty and just letting it go and getting it repaired under the warranty in a few years

I wouldn't wait to have it checked out by your dealer. My dealer thinks they might be going to limit the warranty work to three years, so you might want to be on record with the dealer even if you decide to wait. My dealer does not like doing the warranty repairs because they are not sufficiently reimbursed, so they only service their customers and turn the others away. And then they will only schedule one warranty repair a week, so the warranty repairs get scheduled several weeks out.

For my JT that had these two hinges replaced already and just passed it's 3 year anniversary, I'm going to find something to seal the seam on the door hinges that won't cause warranty issues. I bought some Boeshield that was mentioned in the Gladiator forum and will use that or something similar. My hope is to prevent further hinge corrosion especially because the repainted hinges don't match the existing paint.

 

[NY LI'er]

(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.

Jebiruph,

First, I appreciated your work with the ESS/battery issue. You were truly amazing.

Second, I have seem many pictures of the paint bubbles, and there seems to be three places where they occur.

1. On the hinge by the steel pin.
2. Where the Door/hinge meet usually on the door but sometimes on the hinge
3. Near the lower most part of the doors and hood.

It seems to be part galvanic corrosion and part poor prep/paint, my best guess.

With regards to the paint bubbles on the hinge by the steel pin, the contact point of different metals is where the pin flange touches the hinge. There does not seem to be any solution to "separate" this contact with a spacer, be it plastic or sacrificial zinc.

The use of the Delrin hinge liner/bushing Kentrol part #70012, separates the hinge steel pin from the part of the hinge that attaches to the frame. What metal is that part of the hinge? I am not seeing corrosion on that part of the hinge on many photos uploaded on this forum. I am guessing that part is made of steel. This plastic hinge liner/bushing, therefore, may not be doing anything as it is separating steel from steel? Also use of zinc plated washer at the bottom of the hinge may be doing the same, separating steel from steel? the only solution to inhibit/delay corrosion in this location may be use of corrosion inhibitors such as Boshield or Ultra Tef-gel on the pin? and also perhaps breaking the paint in the "gap" between the flange and the hinge to let the moisture "out"?

With regards to the steel torx bolt used to affix the hinge to the door, someone suggested usage of a plastic washer under the bolt head to separate from the hinge to reduce galvanic corrosion. And usage of ample Boshield or Tef-Gel on the rest of the bolt as well as the steel nut and nut retainer may also be helpful?

Someone from Germany (I think) said he sprays WD-40 on and around the hinges once a month in attempt to keep moisture away, with success till this point. What is your thought on this?

 

[Jebiruph]

Jebiruph,

First, I appreciated your work with the ESS/battery issue. You were truly amazing.

Second, I have seem many pictures of the paint bubbles, and there seems to be three places where they occur.

1. On the hinge by the steel pin.
2. Where the Door/hinge meet usually on the door but sometimes on the hinge
3. Near the lower most part of the doors and hood.

It seems to be part galvanic corrosion and part poor prep/paint, my best guess.

With regards to the paint bubbles on the hinge by the steel pin, the contact point of different metals is where the pin flange touches the hinge. There does not seem to be any solution to "separate" this contact with a spacer, be it plastic or sacrificial zinc.

The use of the Delrin hinge liner/bushing Kentrol part #70012, separates the hinge steel pin from the part of the hinge that attaches to the frame. What metal is that part of the hinge? I am not seeing corrosion on that part of the hinge on many photos uploaded on this forum. I am guessing that part is made of steel. This plastic hinge liner/bushing, therefore, may not be doing anything as it is separating steel from steel? Also use of zinc plated washer at the bottom of the hinge may be doing the same, separating steel from steel? the only solution to inhibit/delay corrosion in this location may be use of corrosion inhibitors such as Boshield or Ultra Tef-gel on the pin? and also perhaps breaking the paint in the "gap" between the flange and the hinge to let the moisture "out"?

With regards to the steel torx bolt used to affix the hinge to the door, someone suggested usage of a plastic washer under the bolt head to separate from the hinge to reduce galvanic corrosion. And usage of ample Boshield or Tef-Gel on the rest of the bolt as well as the steel nut and nut retainer may also be helpful?

Someone from Germany (I think) said he sprays WD-40 on and around the hinges once a month in attempt to keep moisture away, with success till this point. What is your thought on this?

I just got my 5 replaced JL hinges back from the dealer and confirmed that all of them are corroded starting from the pin flange. This is likely due to water seeping into and getting trapped in the gap between the pin flange and the hinge.

I picked up some needle tipped bottles https://www.amazon.com/dp/B07NKSLFSR?psc=1&ref=ppx_yo2ov_dt_b_product_details to facilitate applying some Boeshield into the gap to prevent water from getting into the gap. I tried removing the paint over the gap to open it up, but that did not go well and I do not believe it is practical.

As to the Delrin hinge liners, at the very least they eliminate the metal pin liners which have become a source of corrosion over time on previous Wranglers. They also electrically isolate the steel hinge pins from the rest of the body, minimizing any galvanic electrical pressure that might result from the accumulated steel exposure. And for those interested, the part of the hinge attached to the frame appears to be aluminum (non magnetic).

Here's a pic of corroded hinge pin liners from a 2013 JK.

For the zinc plated washers, I now see that they will not act as a sacrificial anode to prevent the aluminum hinge from corroding. They might relieve the galvanic interaction between the steel pin and aluminum hinge by providing a more susceptible galvanic target, but I haven't seen any discussion addressing this theory.

The door hinge Torx bolts have a tapered head, so I'm not sure how well a plastic washer will work. My plan is to use dielectric grease under the bolt heads.

For treating/sealing the hinge gaps that can trap water and promote the surface corrosion that occurs starting from around the hinges, my plan is to seal them with Turtle Wax Pro Flex Wax. I started waxing with it last year and it lasts for months. I'll put enough on the hinges for it to flow into and seal the gaps before I wipe and buff it off. I'll reapply as needed.

I still pondering what would be a good solution for the door and hood edges.

 

[NY LI'er]

I just got my 5 replaced JL hinges back from the dealer and confirmed that all of them are corroded starting from the pin flange. This is likely due to water seeping into and getting trapped in the gap between the pin flange and the hinge.

I picked up some needle tipped bottles https://www.amazon.com/dp/B07NKSLFSR?psc=1&ref=ppx_yo2ov_dt_b_product_details to facilitate applying some Boeshield into the gap to prevent water from getting into the gap. I tried removing the paint over the gap to open it up, but that did not go well and I do not believe it is practical.

As to the Delrin hinge liners, at the very least they eliminate the metal pin liners which have become a source of corrosion over time on previous Wranglers. They also electrically isolate the steel hinge pins from the rest of the body, minimizing any galvanic electrical pressure that might result from the accumulated steel exposure. And for those interested, the part of the hinge attached to the frame appears to be aluminum (non magnetic).

Here's a pic of corroded hinge pin liners from a 2013 JK.

For the zinc plated washers, I now see that they will not act as a sacrificial anode to prevent the aluminum hinge from corroding. They might relieve the galvanic interaction between the steel pin and aluminum hinge by providing a more susceptible galvanic target, but I haven't seen any discussion addressing this theory.

The door hinge Torx bolts have a tapered head, so I'm not sure how well a plastic washer will work. My plan is to use dielectric grease under the bolt heads.

For treating/sealing the hinge gaps that can trap water and promote the surface corrosion that occurs starting from around the hinges, my plan is to seal them with Turtle Wax Pro Flex Wax. I started waxing with it last year and it lasts for months. I'll put enough on the hinges for it to flow into and seal the gaps before I wipe and buff it off. I'll reapply as needed.

I still pondering what would be a good solution for the door and hood edges.

Thank you for letting me know that the hinge part attaching to the body is of aluminum. With that information, then it would make sense to separate it from the hinge steel pin with the stated plastic liner, in an attempt to minimize electron movements.. The zinc plated washer at the bottom may also help in that regard.

The other point of contact between the steel pin flange and the upper/outer part of the hinge is still an issue. Perhaps a sharp cutting tool to open the gap, especially without underlying corrosion, in hope to minimize water retention may still be something to consider.

There is a rumor that FCA may be placing some sort of zinc shim between the door and the hinge in newer 23/24 models. Is this a verified information? If not, as a preventive measure, what do you think about taking the hinge off and protecting the unfinished surfaces (of both the door and hinge) with some sort of prep, be it paint primer or epoxy sealer and/or placement of home made plastic shim, in hope to reduce electron movements? This in additional to ample usage of Boshield/Tef-Gel?

As to the method of keeping moisture away from all the above parts, be it wax as in your case, or WD 40 in others, can only help, I would think. But I think some may have better penetrating ability to get into tight spaces.

 

[NY LI'er]

I just got my 5 replaced JL hinges back from the dealer and confirmed that all of them are corroded starting from the pin flange. This is likely due to water seeping into and getting trapped in the gap between the pin flange and the hinge.

I picked up some needle tipped bottles https://www.amazon.com/dp/B07NKSLFSR?psc=1&ref=ppx_yo2ov_dt_b_product_details to facilitate applying some Boeshield into the gap to prevent water from getting into the gap. I tried removing the paint over the gap to open it up, but that did not go well and I do not believe it is practical.

As to the Delrin hinge liners, at the very least they eliminate the metal pin liners which have become a source of corrosion over time on previous Wranglers. They also electrically isolate the steel hinge pins from the rest of the body, minimizing any galvanic electrical pressure that might result from the accumulated steel exposure. And for those interested, the part of the hinge attached to the frame appears to be aluminum (non magnetic).

Here's a pic of corroded hinge pin liners from a 2013 JK.

For the zinc plated washers, I now see that they will not act as a sacrificial anode to prevent the aluminum hinge from corroding. They might relieve the galvanic interaction between the steel pin and aluminum hinge by providing a more susceptible galvanic target, but I haven't seen any discussion addressing this theory.

The door hinge Torx bolts have a tapered head, so I'm not sure how well a plastic washer will work. My plan is to use dielectric grease under the bolt heads.

For treating/sealing the hinge gaps that can trap water and promote the surface corrosion that occurs starting from around the hinges, my plan is to seal them with Turtle Wax Pro Flex Wax. I started waxing with it last year and it lasts for months. I'll put enough on the hinges for it to flow into and seal the gaps before I wipe and buff it off. I'll reapply as needed.

I still pondering what would be a good solution for the door and hood edges.

Would usage of nylon spacer washers for the hinge screw be practical? they may be flexible enough to bend slightly under the graduated screw head? Would you know what size washer that would be, since you have the hinge and the screws for measurement (looks about the same size as the the zinc plated washers you mentioned for bottom of the hinge) ?

how about also using the nylon washers at the bottom of the hinge instead of zinc plated steel washers? size m10 20 mm diameter size?

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