|The MGA With An Attitude
FASTENERS, CORROSION RESISTANCE - RT-105
At 04:24 PM 10/7/04 -0600, Henry Speer wrote:
>" I have a ton of rusted nuts & bolts. I am able to clean these up in my sand blast cabinet quite well. What I am concerned about is if I put the bare steel bolts & nuts back in they will rust up in no time. "
Yes? So what's the problem there? If this is to be a concours restoration, that's the way the car is supposed to be built. That's exactly the way it came from the factory.
>"Is there a preferred treatment to prevent future rusting?"
Well, yes. By concours standards, the prefered treatment would be to use bare mild steel fasteners, paint after assembly, and then forever keep the car in an environmentally controlled clean room with constant temperature and low humidity. But that's why I'm not a concours buff. I like to drive my MGA.
>"Painting is no good as it gums up the threads and will not last that long anyway."
If you do anything other than paint the thing after assembly, you violate the consours rules. Mind you, that doesn't bother me one bit, as I'm not the least bit interested on concours. If you are going to ignore concours reatoration and do something non-original, then there are no rules or guidelines, and you do anything you like.
I'm not that particular. I just slap a little anti-seize on the threads and paint it after assembly. I don't find any problem with the paint gumming up the threads. How often would you plan on removing the fenders after it's finished? The first time I disassembled my MGA for reatoration the car was 19 years old with 150,00 miles, and I broke more than a few rusted bolts. With restoration I had all of the bolts chemically cleaned and reused most of them. The body was painted in pieces. The bolts were generally installed bare, with a touch of antisieze, and painted over after assembly. For the most part I find that the bolts which were painted on both ends (fender bolts) were fine after years of use. After 12 years and 125,000 miles I had the wings off for another repaint. The fender bolts came right out and didn't break one of them. The paint peeled right off the threads as the bolts were removed, no problem. Similar experience also with removing suspension parts after years of use.
The fasteners I have trouble with are the ones located where there is no access to paint the threaded end after installation (or to paint the nut). The prime offenders are those that screw into the box section of the door posts. The door hinges and buffers and latch strikers have removeable nut plates in slide pockets. If those screws are buggered up you can drill them out in a pinch and replace the tapping plates. The real killers are the screws holding the rag top folding frame. Those screw into totally inaccessible floating cage nuts inside the door post, and they are VERY prone to rusting on the tip end of the screws. It was a cut and weld for repair for restoration, and again cut and weld for replacement 12 years later. I now have a solid steel tapped plate there with stainless steel screws and gobs of antiseize in the threads.
>"I did try treating one large bolt with a gun bluing solution. It worked very well, giving a nice dark blue finish which should give some rust protection. Any thoughts on this problem?"
There are plenty of different approaches to slowing rust on fasteners, some more expensive than others, and some less effective than others. I don't suppose gun bluing would hold up very well to long term environmental exposure. It might be one step less effective than black oxide.
Bear in mind that captive threads in the car body (fender mounting) are still going to be mild steel, unless you rebuild a substantial part of the body and frame to incorporate only stainless steel material for all captive female threads. Assuming that you don't rebuilt the entire body out of stainless, that would require welding stainless fasteners to mild steel parent parts.
The only reasonable approach I can think of for the captive fasteners is to paint the body in separate pieces, then chase out all the female theads with a tap. Maybe assemble using some form of corrosion inhibitor in the female threads (anti-sieze may be sufficient), and paint it again after assembly (at least around the fasteners). How else could you possibly keep the female threads in the body from rusting?
If you use anything other than plain steel screws you have to contend with galvanic corrosion with dissimilar metals. For best corrosion resistance then you might consider tossing all of the original fasteners into the trash and replacing them with stainless steel fasteners.
If the used fasteners you have in hand are mostly in good serviceable condition, you might consider having them nickle plated. For a single batch order I don't know if nickle would be much more expensive than any other type of treatment. When you pay a plating shop for a couple hours work, the cost of material may be small by comparison to the labor charge.
But even using stainless or plated fasteners, you probably still need to use anti-seize on the threads for assembly, and paint over them afterward to protect mild steel body parts.
Perhaps you would like to define what level of corrosion resistance you're after, and how much you're willing to pay for it (other than wanting perfection for free).
Mind you, concours rules are downright strange, and they can vary according to venu.
For some concours judging, the car has to be reproduced exactly as it left the factory, and being over-restored is a no-no. For instance, you would be required to assemble the body with bare steel panels and bare steel fasteners, and paint it in assembly (except to attach the fenders after painting). Among other things, this means you are not allowed to paint 4 out of 6 surfaces in the body sills, or the inside of the door posts. But you could paint or rustproof those surfaces in areas which will be totally hidden from view, so the judges can't see it. You could generally get away with using any mateial for the fasteners in areas where they are painted over (although the heads should be the correct vintage style) or are hidden behind trim panels. Where the car frame or radiator were originally "chassis black", you would not be allowed to use gloss black paint. Where body is mated to frame, I believe the original fasteners were left as unpainted mild steel, so the only truly acceptble surface there would be rust. Ditto for the master cylinder and windscreen wiper motor.
For another concours venue it may be acceptable to over-restore a bit. You might be allowed to use gloss black paint, or to polish the carburetors and copper pipes to a (very non-original) bright finish. You may be allowed to paint every surface of every panel inside and out, including dip painting to get inside the door posts and sills. But the same concours judges who may allow you to paint the body to frame fasteners (very non-original) may deduct points for using bare stainless steel bolts in the same location. Like I said, the logic can be wierd. Perhaps they allow that touching up the paint and polishing things is a plus for prettying up the car for a concours show, but changing materials is a no-no.
Here's a good question to get you started in the ballpark. Are you willing to spend $1000 extra on the restoration specifically to reduce corrosion of threaded fasteners? I once had an idea that it could be possible to individually brush plate the female threads in the body (which would take a long time of course). That way the body threads might be nickle plated the same as the bolts, and no corrosion problam at all. Just a thought.