Rust protecting your car

[Mux213]

Hey Guys,

Since this keeps popping up again and again, and some people are busy with restoring their cars, let's talk abit abotu rust protection and properly painting your car.

Here is what I think of it from what I've read so far and based on my preperation work for the RX7:

First, stripping off the old paint layers.
Wirewheeling will only remove surface rust but always leaves visible or invisible rust behind.
Sandblasting is the prefered method that is still somewhat affordable, but even sandblasting can't get into hard to reach areas or can even damage the body work as its a pretty aggressive method or stripping paint.
Expensive but definately the best way (often done after getting most of the paint off by the forementioned methods) is to submerge the bodywork in an acid. Combined with an electrolitic process this removes EVERYTHING from the body work. The moment the body comes out of the acid bath it is completely clean. However 1 second later microscopic rust already forms, so even with this method getting the body primed asap is very importent.

Rust makes rust (rust is a catalist for the rusting process), any rust left underneath your paint job will soon cause more rust to develop. So lets look at the options once you have your car clean of the old paint and relatively rust free.

The most used with car restauration is just to apply a layer of primer. Primers main job is to uniformly coat the car in such a way that the color layer can stick to it very well. Normal color paints don't adhere that well to steel. In the early days this was even so that the primers used where porious because the top coat stuck better to it. It was the top coat that closed the steel off from harmfull outside air! Using an old primer and waiting with the topcoat for a couple of days was a sure bet to get a major rustproblem within weeks.

Today most primers completely seal the steel from harmfull influences however you still need to worry about what was already there. If (invisible) rust is already on your body work (which in 99% of the cases is so) it will find a way to continue rusting nicely underneath your perfect primer layer This is why most primers these days contain etching qualities. This causes any microscopic rust to be 'neutralized' (convert rust molecules into something harmless by a chemical process) however larger chuncks of rust is to much for it to handle.
Also something to keep in mind is due to environmental reasons, most new primers use water based solvents. They evaporate moisture to cure. When you use such primers in a normal DIY environment the curing process takes a relatively long time and the evaporated moisture itself could become a source for rust to develop.
In the end, sandblasting your car, painting it with a good etching primer preferably in a heated environment, keeps your car rustfree for years. Even in DIY conditions there is a good chance you wont see rust for many years.

If you've wirewheeled your surface you can also go the fertran route, fertran is a substance that also neutralizes rust, but you have to wash it off afterwards and then use a primer but it gets your body work into a state where the etching compound in a primer is enough to handle whatever is left behind. Fertran works similar to an etching compound converting any left behind rust into something harmless.

Then you have products like POR15 or Rustbullet that come out of tests very very good. They are chemical based primer coats that cure on moisture instead of evaporating moisture. They also penetrate the rust layers and adhere to the steel surface underneath the rust effectively closing the steel off to outside influences. They also keep moisture away from the steel during the curing process as the moisture is used for the curing process. But they are much $$$, probably one of the most expensive ways to treat your car in a DIY manner.

Last but not least, the most effective way known to me is galvanising (or zink coating). No I don't mean those cheapo zink spray cans you can get at your DIY store. This is a process that continues on the acid bath process. In the acid bath electric current is added to 'extract' the oxigen attoms from the rust molecules (electrolitic process). Right after this process the body is moved into another acid bath where the current is reversed and zink is added. The zink electroliticaly adheres to the steel giving a life long protective layer to your steel.

Interestingly enough, I've been trying to get in touch with a guy that claimed on the internet that he did a DIY version of this process for a frame of an MG. Our hachi's are to big (you'd have to build a kickass tank) but an MG frame (or a Delorean frame for that matter) is small enough to create a low bath that holds a salt watter solution. This wont 'eat away' at paint like acid does, but it does allow you to do electrolitic process to treat the rust and then galvanise the frame.
There is one major issue to overcome here. Its highly illegal to do this process at such a scale (anyone can buy small galvanising kits to galvanise cutlery and small metal items like coins).

Owh, a friend of mine has a quote out on doing this process at a company for his Delorean frame, costs around 5000 euros. Doing a hachi probably goes over 10.000 euros.

[The Doctor]

i don't know all about it, but a friend of mine toldme that sandblasting with the paint still on isn't a good idea.

Because the paint is very hard (in most cases ) they need to use a big pellet, just to 'come through the paint'. This is not ideal for the bodywork, because there is a chance that the sand just blows right trough it.

@ parts wich have some rust, that isn't a problem, but even good parts of the body may be damaged, and that is not wat you want.

He told me, for a proper sandblast job, you have to sand the whole body first, so that there isn't any paint on it, and then sandblast it (with a much smaller pellet), so that the good parts won't be damaged to bad.

[Mux213]

Hey Doctor,

You have a valid point there I think. I know how much work it was removing the paintjob with a wirewheel on the RX7. It also shows how good a profesional/factory paint job is compared to a DIY paint job which often is much easier to remove.

But in the end, sandblasting is a dangerous process. If not done correctly, you can blast right through your body work. Starting with sanding your car down to bare metal and finishing off with sandblasting purely to get the rust off sounds like a sound idea.

[Ivan141]

Wow....nice write-up Mux! Brings up many interesting points for me since I want to get rid of quite a few rust spots. Lets take my "new" doors for example. They have some surface rust on the outside which is very difficult to remove, the rust has eaten in, creating a rough patch that doesnt go through the sheet steel completely. Sandblasting it with smaller particles might do the trick without going completely through the bodywork, but remains risky. Then there's the rust converting substances approach, but the problem is that it is a very uneven surface, which might not be completely cured using such a substance.
On the bottom welds there are a few rust spots as well, as on every other door that hasnt been treated yet. Sandblasting seems to me a better way of stopping that rust.
What would you think is the best method of effectively stopping rusting to continue on sheetmetal, and especially the welds on it. The method of bodypanel welding is VERY prone to rusting on ae86's, just take a look at the rear body section above the rear licht clusters, ugly overlap welds everywhere.

[Mux213]

Ivan,

I'm not sure about that because I don't know that much about welds. My guess is that welds themselves are fairly dangerous because bad welds can rust from the inside out, not matter how good you've treated the outside. If the rust is on the outside then its a matter of getting rid of the rust and neutralizing any invisible rust (smaller then the eye can see).

My guess would be sandblasting and then soaking it in fertran (and leaving it for atleast some hours) to get to the areas the sandblasting doesn't get to (actually I think wirewheeling would be good enough here and less risky to damage the welds) and then priming it. Yes you will have a rough surface but you can fill that with epoxy and get it smooth again.

But do keep in mind, what I wrote up here is what I've read on the internet and discussions I've had in other forums. I hope to get my story challenged by someone here who has more hands on experience then I have So far I've only done extensive work on my RX7 with mainly POR15. I must say that so far I haven't noticed rust returning, even on very badly rusted parts. I'm gonne be using POR15 on my spare axle aswel since there is no way I can remove all the rust (not is it important to in this instance).

I must say one thing that springs to mind, my friend who is doing the body work for me has changed the hood on his car by welding parts to it, very cool result. Anyways, he melted tin on the affected areas to fill up the holes and stuff. Sorta like the lead lining that was used on Discovery channel when they fixed up that e-type jag

Btw, nice thing to know that I will be taking pictures off. On the right bottom of my rear window I found a nasty point of rust. We'll be taking the rear window out and then cutting part out of the window frame. Instead of welding a piece of steel in, we'll be glueing a piece of steel in! According to theory this is actually stronger then welding. At the repair shop my friend works at they are starting to glue more things together then weld them together. Leaves much cleaner and stronger results.

[Ivan141]

That tin filling of surface inperfections sounds cool...does that hold up well? What kind of tin are we talking about here, when I hear melting tin the term soldering immediately pops up in my mind.

[Mux213]

Don't know, I'll ask him on tuesday when we're gonne be fixing up the dent in my car...

[s.bjelke]

I use microscopes to detect rust. Here in norway I get a x30 microscope(pocketsize) for 300NOK ($45)(35EUR). With this I go over the surface after sanding down. I get every spot of rust this way

[Jan Pedersen]

s.bjelke Wrote:I use microscopes to detect rust. Here in norway I get a x30 microscope(pocketsize) for 300NOK ($45)(35EUR). With this I go over the surface after sanding down. I get every spot of rust this way

That sounds like quite a bit of work! But Im sure it works

[robokill]

Rust

Every hachi has to suffer on it

Mine is pretty clean now but still you will have to spent around 8000 euro's on the body if you want it to be perfect :-(