Factory roof rack rust cause found?

[jpoole]

I recently pulled my factory roof rack for inspecting and rust treatment and believe that I may have found a leading reason why the factory rack mounting points often rust out so badly. It looks like water flows in from above and then gets trapped inside the rack feet. See what look like water lines on the inside of each foot in the first picture below for evidence of the water pooling.

It seems like the mixed metals of the roof and rivet nut poorly painted/sealed after install and then soaked in a captive water bath is why these often suffer so much from corrosion.

My roof and the rivet nuts were still serviceable so I ospho coated them and then added sealant to keep water out from above. I also added a drain on each foot to let water out if it does get in there at some point. I may keep the rack long-term since I don't need/want to put much weight up on the roof band I'm optimistic that the rust risk is mostly gone now thanks to the sealing and drains. The following picture shows the drain that I cut with a triangular file.

Anyone else come to this same conclusion or seen similar waterlines inside the feet?

 

[cme4lyt]

Damn, I wish the PO had seen your post before I found this.....

 

[rolliges]

Wow, did that drain out of the sunroof drains?

 

[fz1boxer]

i am almost afraid to tackle mine,one of the PO's put in a bolt that won't come out,pretty sure its cross threaded.
i plan on pulling and inspecting to see if i need to do any repairs but right now i see no water leaks.

 

[jpoole]

@cme4lyt ! whoa, that's pretty intense and scary!

If the front of one of your tracks/runs (whatever they are called) rusted that badly then obviously a captive pool of water isn't necessary as there is not a foot surrounding that area. The hole near your foot looks like it could be from the foot wearing through the paint to expose bare metal. I saw some of that on mine as well, just without the rust.

I'm sure water, dissimilar metals and poor sealing were at play in your rust holes but perhaps also salt spray on your truck helped? How is the undercarriage on that rig? The way that I understand it, salt residue pulls moisture out of the air and will keep a surface damp/wet over time which is at least one of the ways that it accelerates rust. Seems like you would need something like salt or living in a really wet climate to get that much rust but I guess that once it starts it never stops and that's what happens given enough time. Hope the repair wasn't too tough.

 

[paulzak]

It's a really poor design, made to look good and support nothing.

 

[rolliges]

The hatch wing supports pool water too and cause rust too. Take a peek.