Aluminum Floor Pans

[rztmartini]

The rust on the floor of my car is worst where the passenger feet rest. would it be a bad idea to cut out from up there down to where the seat mounts and rivet in aluminum sheet instead of welding in a new floor? it isnt the entire floorpan, so I dont think there would be much structure support there...but im not an expert.

 

I plan on just making this a sound DD car, cause its got a lot of rust already. Maybe later on ill be looking for a better body to swap all my parts onto, but for now im cheap...

 

Another possible fix:

My grandpa used this while restoring a 69 porsche 912. fiberglass with por-15 instead of resin over the rust holes, put aluminum over the fiberglass, spaced about .5" to .75" over the fiberglass and fill the gap with a foam. This gave it good support, and gave a good sound-deadening effect as well. would this be worth the effort in the Z?

[mikeatrpi]

I'd weld. But you probably don't have one / can't, otherwise you wouldn't be asking this question.

 

In that case, look into panel adhesives. You can glue the floor together. With a couple screws / rivets till it sets you will probably be OK.

[rztmartini]

well i can weld, but i thought that lightweight might be a little more beneficial. plus, aluminum sheet is cheaper than some new floorpans.

[dosquattro]

I don't think the weight loss in the plate would be more beneficial then what welding in a steel pan would give back some rigidity to your already flimsy 35 year old chassis. Just my .02.

[Chaparral2f]

Personally, I'd weld in steel. I thought of doing aluminium floors and firewall in my Z31, but decided against it.

First, riveting in aluminium panels is extremely labor intensive especially if you expect any strength.

Second, joining a ferrous and nonferrous metal can cause more problems than they are worth. Over time steel will react with aluminium and can cause the aluminium to corrode. Just my two cents.

[EMWHYR0HEN]

If you just want to replace the rusty area without changing the entire panel, I would just cut out the rust and replace with sheet metal ,and WELD it if you have access to a welder.

 

after I'd make sure you protect the rust from spreading.

[buZy]

I did alum floor pans. But not to fix a rust problem. Did it to lower the seating, interior trans x-member support, and increase overall 3D structure. Yes very labor intensive indeed. The strength in most surface situations is much stronger than welding to thin sheet metal. Ferrous and nonferrous metal is not a problem. I have used alum all over the car in many places for many years now with zero corrosoin problems. It's really not an issue. Pics in my hybrid galley show many areas of use. (Seat pans, fuel box, sub frame connectors, rear hatch tailgate support.)

http://album.hybridz.org/showgallery.php?cat=500&page=3&ppuser=10889

 

For your rust problem though. I would weld in some steel new floors. You could riv in alum and seal it up and it would work great. Though most people looking at your car for resale would think it was a hack job when it's not. People are stupid sometimes, like welding is king or something. Too much pimp my ride tv. If a Z was build using rivets instead of spotwelds just think of the cost factor. Yes the weight but most weld stitch there car too so go figure the real weight. Too exotic. Built like a real aircraft, like a WWII Jap Zero. The abilty to maintain/replace joints and substructures and spreading out the load in joints, far superior. Ok guys don't kill me now. Each process has its own positive and negatives sides. I just see many doing restoration falling into "I have to weld it" when other alternatives could be implemented with better success.

[Zmanco]

I'm reading this thread with a lot of interest because I need to replace the front half of my passenger side floor pan. I do not have a welder nor welding skills, and had just assumed that welding was the only option. But I think I'm reading here that using aluminum which is riveted and bonded is an acceptable, maybe even stronger alternative?

 

Does this require others special tools and skills? I'm thinking this might be a better way for me to make this repair in my own garage with my own hands. Or am I missing something.

[Dayz]

This is a No-no. Read on what aluminum and metal does together...yes in a good environment it works well. As a floor pan, your alu will make your metal rust a lot faster and everything will be a redo in a year or so. You are a lot better grinding, and welding a new sheet metal...it doesn't have to be perfect, but effective. It will take you a day and you will be over and not thinking of redoing it next year!!

 

Dayz

[Zmanco]

Dayz, you're correct: I googled steel aluminum corrosion and found a lot of info on the corrosion to be expected with steel and aluminum in direct contact. If the boundary between them can be kept dry, then it's ok, but that's not likely on the floor of a car.

[antimanifesto09]

Another possible fix:

My grandpa used this while restoring a 69 porsche 912. fiberglass with por-15 instead of resin over the rust holes, put aluminum over the fiberglass, spaced about .5" to .75" over the fiberglass and fill the gap with a foam. This gave it good support, and gave a good sound-deadening effect as well. would this be worth the effort in the Z?

 

Anyone with any thoughts about this method?

[Zmanco]

Here's a discussion how BMW attaches aluminum to steel.

 

http://www.i-car.com/pdf/advantage/online/2003/111003.pdf

 

Looks like it takes special preparation of the surfaces along with special rivets and tools.

 

[rztmartini]

okay, so aluminum directly on steel is a no-no. BUT...what if you POR-15 the steel, then rivet the aluminum (or get stainless button-head screws), then POR-15 that so seal it and put a little deadening so that it doesn't vibrate at ceartain frequencies?

[Z-TARD]

I think that by riveting the aluminum to the steel, you'd be losing most of the benefit of the POR 15. The corrosion between aluminum and steel is a result mostly of electrical action between the two metals. By painting with POR-15 and then bonding/gluing them, you are isolating the steel from the aluminum. Riveting through the two metals would re-establish an electrical connection, and you would likely see corrosion start at the rivet points later on.

 

I think gluing new floor pans in could work, but the fitup of the new pans would have to be pretty precise to keep the glue layer thin for maximum strength. I'd suggest using high strength magnets above and below the floor boards during gluing to clamp the pieces together.

 

Having said that though, my prefered method of repair would still be to weld in a new set of steel pans

[dj paul]

i second just cutting the rust out and welding sheet metal. Thats the best route. I ordered totally new floor pans for my first Z and soon discovered i could have done the same thing with sheet metal after cutting them up so many times.