Jeep Wrangler JL Corrosion

[DKAwildcat]

The current Jeep Wrangler is fabricated with aluminum body panels without any non conductive isolation material between them and steel materials (such as door hinges). Owners are now experiencing bubbling of paint as a result of galvanic corrosion. The remedy being provided by Jeep is to repaint the corroded areas; however, this does not stop the corrosion from happening again. I was wondering if a third metal, such as magnesium, could be attached to the steel frame to act as the sacrificial anode so as to prevent corrosion between the steel and aluminum. Thanks in advance for your answers.

 

[3DDave]

The use of a sacrificial material is useful when the item being protected is in the same environment as the sacrificial material - example, a hull of a ship in the corrosive liquid of salt water can be protected by exposing a more reactive material to the salt water.

If one were to interpose the magnesium across the steel to the aluminum that might work except the corrosion products would soon insulate the magnesium and it would stop working.

It really requires galvanic isolation and corrosion protection.

I haven't used it but I've seen reported good results from a trusted source for a product called "fluid film" being used in a place where 5 years appears to be a long life for a steel frame vehicle due to the continuous use of large amounts of salt on roads during the winter.

Keep in mind that aluminum itself is a reactive metal and a poor paint job won't protect it. This is why aircraft are painted with a zinc chromate primer, not as a direct sacrificial material, but as a surface protectant over an alodine pre-treatement.

 

[TugboatEng]

The bubbling of paint is not so much a galvanic corrosion problem but a crevice corrosion problem. Aluminum under paint is very sensitive to corrosion because they paint prevents the aluminum from forming a protective oxide layer.

A chromate conversion coating can help protect the aluminum under paints. I believe there are some brush on coatings marketed under the brand Alodine.

Otherwise, keep the surface as clean as possible and don't allow dirt or grease to accumulate as these also create the same crevice corrosion conditions. A mild acid such as citric acid can help remove salts and contaminants.

 

[EdStainless]

This is a case where paint makes things worse.
Largely because there is no 'tight' paint job, there are always pinholes.
Isolation would have been the right thing to do.
What also works is putting the transitions where you can cover them with a more robust coating.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[enginesrus]

Can't be fixed. They are not allowed to use a quality paint nor can they do it correctly.
I suggest talking to Boeing about the correct paint and methods to use.

 

[BrianPetersen]

Quite a few other vehicles are built with aluminium panels, often bolted to steel structures underneath or to steel hinges or the like, and are not experiencing this problem. Perhaps it's something specific to the way that particular vehicle is being built.

 

[SwinnyGG]

Perhaps it's something specific to the way that particular vehicle is being built.

I have direct experience with Chrysler's paint shop equipment, materials and procedures... without getting into too much detail, they are not installing painted coatings with the same standard of quality used by their competitors.

As an example: the aluminum body panels on F150s are not connected to their steel frames or sub-frames in any special way, and yet there is not really an particular difference in paint durability between a new aluminum F150 and an old all-steel one. Because they are painted using processes/procedures/materials that provide a certain level of quality.