Rear Seat Belt Corrosion!

This looks like the galvanic corrosion on my boat. Never expected to see it in a truck. Have you sprayed white vinegar on it as a mitigation?

 

I tried some white vinegar on it, which seems to help remove the rust. At this point I need to fully pull off the seat belt connector bolts, and remove the seat belt straps so I can clean off the seat belt receptors as well. New thread with this process is inbound as soon as I can get around to it. I intend to take lots of pictures as well.

 

Oh yeah, galvanic corrosion in my boats as well, would NEVER expect this in a Tacoma. I'm appalled, honestly.

 

Yeah this needs a new thread for sure. This type of corrosion caused me 40k in boat repairs; it's nasty stuff.

Do you have any stray current in the frame? Any kind of electrical potential across dissimilar metals is an indicator Galvanic or electrolytic corrosion can/will occur. If these connectors are really zinc or zinc plating that would strongly indicate they're acting as an anode and being "sacrificed".

I wonder if this is as simple as steel bolt, aluminum frame with no rubber gasket or coating between them.

 

My thoughts exactly. I wonder if it's as simple as the dissimilar metals issue. I don't know how to check for a stray current issue though

 

Another update: The dealer is now quoting me $770 pre-tax to get the parts replaced. Needless to say, I'll definitely be working on this myself!

 

In a boat you can just compare the water to the metal in question using a multimeter. I _think_ for galvanic corrosion you can just measure DC voltage between the two metals. I think you could also do a diode test to figure out which is the anode, if any.

Gotta be honest though. I'm coming at this from a salt-water wood-boat angle and that's mostly electrolysis damage and it's all voodoo and black magic.

 

They use zinc plating on structural steel parts like seatbelt anchors and such because it acts as an anode and sacrificial barrier to galvanic corrosion while protecting the steel underneath. The zinc will convert to zinc oxide or zinc hydroxide when reacting with oxygen or water in the presence of voltage potential. Dissimilar metals often have a voltage potential between them. Usually zinc oxide is a rough, white scale on the surface (sometimes called white rust, though its not rust and has nothing to do with iron/ferrous metal) and zinc hydroxide is a buildup of white flake/crystal like stuff which might be evidence that moisture is getting to that area. The rusted seatbelt reels is another hint. The good news is that when zinc corrodes like that it's because it is acting as the galvanic cell instead of the steel that it's plated on exactly like it was intended to do. Still, it should be cleaned up and the bracket inspected for pitting and material loss of the base metal (steel). If you knock off the white fuzzy looking stuff and find a thin, rough, white-ish surface over the steel and the steel looks to not have lost and chunks or pits, then it's probably structurally sound. That being said, you have lost much of or all of the sacrificial barrier and if the condition causing the corrosion persists or something else happens in the future that causes further corrosion, it may be the steel that is damaged next time.

It would probably be a good idea to look at the area around it for other corrosion, under the truck in that area, etc. If moisture from a leaking window, 3rd brake light, etc is making it's way in there, it's probably getting to other places around there, too. Being in SLC, I doubt that corrosion is from just general humidity and moisture in the air.

Edit: here are a couple sources with some not super nerdy info about zinc being used as a corrosion mitigation metal.

https://www.dorsetware.com/how-does-zinc-plating-stop-corrosion/

https://www.sharrettsplating.com/blog/corrosion-resistance-of-zinc-plating/

 

Thanks folks.

 

I wouldn't think it is a dissimilar metals issue considering many people don't seem to have this issue (myself included).

 

An electrolyte is still required for dissimilar metal corrosion to take place. Just having dissimilar metals, even those with high potential (stainless and aluminum for example), still requires some sort of electrolyte to corrode galvanically.

 

Could this be as simple as having something grounded improperly (accessory or even a faulty OEM ground)?

 

I'm still baffled by all these mysterious issues, leaks, corrosion, strange noises and suspension problems these new Tacoma's when I've put over 200K on several Toyota's manufactured in the 80's and 90's without any leaks, rust or corrosion.

 

something got back there, things like that don't usually happen...i've had cars for 10-15 years and never had that issue, under warranty?, take back to the dealer..

 

I don't have time for any of that.

 

No, I don't think so. The current that drives the corrosion in a galvanic cell is extremely tiny and is the result of the nature of the materials/metals. It's not an electrical system kind of thing.

 

I've pulled off the brackets. Pt. 2 of this journey is here: https://www.tacomaworld.com/threads/rear-seat-belt-corrosion-pt-2.705421/#post-25025916