|Part 1 Causes and where to look||Part 2 Probing for rust and treatments||Home
In the first part of the article, we discussed some of the causes of rust and a few of the locations that you should look for rust. You might think that this is easy, but you cannot always see the rust. It may be hidden by old undercoating, caulking, or asphalt sound deadening material. This means that you must probe to find the rust.
Any sharp tool can be used to probe for rust. An old screwdriver works well on old undercoating or asphalt. Be sure your tools are sharp; dull tools just make the job harder and take longer. On the bottom of your car you are looking for loose undercoating. Jab it with your tool and try to scrape it off You will note that it is usually loose where it was put on too thick. Where the undercoating is stuck well, it absolutely will not come off. Where it is loose, it comes off easily There is no in between and this makes the job easy. Wear old clothes and eye protection when you're doing this because you will get dirty!
The undercoating is there to protect the paint against stone chipping and the sandblasting it gets from the road. It does nothing to prevent rust and serves to cover it up more often than not. It will usually be loose in areas where two pieces of metal are joined, or where there is a sharp edge. The loose undercoating will allow water between it and the metal, and the water will be held there constantly because it cannot drain away.
You must pretend you are blind when you are probing for loose undercoating. The coating may appear perfect and sound, but probing with a screwdriver will find the loose spots. Do this everywhere. Where the coating was loose and you have scraped it clean, use a good brand of metal prep on the bare spots. These phosphate agents will etch the steel and remove small amounts of rust. For the best job when painting bare steel, you should always use one of these agents. You can get them at auto paint stores and parts stores that handle auto paint. "Rust converters" work very well, but they must not be applied where automotive paint will go; only with the special enamels for this purpose. In areas that do not require a fine exterior finish, you can merely use a good rust preventative primer. Just be sure to use a primer; but because a primer is porous, you must next seal it with regular rust preventative paint. Remember; the primer is for adhesion and the paint is for sealing
Next you should apply undercoat once again to the bare areas. Try to keep the application of undercoating light, because when it is too thick, it is more likely to come loose.
Be sure you probe and inspect all areas of the car carefully. You will probably find lots of areas where your probing tool will go right through the metal. Areas like this must be repaired. All of the rusted metal must be cut out. Chances are, when you get to doing this, you will find plenty of rust that you did not know you had. Remain calm. Put aside any thoughts of selling the car or trying to get a better one. Chances are that if you got another car that looked more original it would be in worse shape under the camouflage of undisturbed undercoating.
The most important thing is to remember to repair damage due to rust as soon as possible. If you keep driving the car, thinking that you will fix the rust someday, you will find that the job becomes larger very quickly. Depending on the cause of the rust, a few months can make quite a difference! If you wait too long to get after the rust, your car will be weakened structurally and, soon enough, will not be worth fixing.
Your investigation of the car should include the drilling of holes so you can see inside the enclosed members. You will be surprised at what you find. Under the front seats there is a box section that is enclosed and very difficult to repair when rusted. An inspection hole cut in the floor (after first removing the seats) will allow you to paint and inspect this area. Since it is over the muffler it gets hot, and the heat increases the rusting action. Make a cover from sheet metal to cover the hole when you are done. Sheet metal screws will attach the cover. These inspection holes can be placed behind the kick plate on the lower portion of your doors if you have a Pallas. A vacuum cleaner can be used to remove dirt and rust chips. Be sure to cut an inspection hole in the triangular box section beneath your feet if you suspect you have frame rust.There are only two useful ways to prevent rust.
The other way is by galvanic action, where dissimilar metals are used so that one will corrode and thus save the other. This method works the best, but only works where the dissimilar metals are covered with an electrolyte (water in this case).
Have you ever wondered how they can make large ships of steel that float in salt water yet don't rust through? The answer is large zinc plates that are attached to the bottom of the ship. They rapidly corrode and protect all of the steel below the waterline. They must be replaced from time to time.
The same effect can be seen on your D or SM in the rear suspension. The aluminum alloy cylinders are very electropositive compared to the steel and are electrochemically eaten away in preference to the steel. They corrode very fast and have been known to have holes eaten completely through to the point of a hydraulic leak. They have been so weakened that we know of several that have broken, with the sphere and cylinder half left on the road. This sounds bad, but it does protect the cylinder mounting bracket and the frame. This bracket is the world's best rust trap, but it is not a problem area because of the protection the cylinder offers as a sacrificial anode.
This method of protection by galvanic action is now more fully utilized on new cars by the use of galvanized sheet steel. With galvanized steel, the sacrificial anode is spread over the entire surface of the sheet. If the zinc coating is scratched, it will still protect the area and the scratch will not rust. If the steel were merely painted, stone chips or scratches would begin to rust very quickly. This is because paint works by sealing, while the zinc protects by going away first. Galvanized sheet steel has not been used in the past for automobiles because of problems with welding and painting. Remember, the zinc corrodes away to protect the steel. So, how can you paint the zinc?
Most of the new cars made today, including Citroen, now use special zinc-plated steels or 'one-side' zinc-coated steels and special paints. Zinc-plated metal would seem to be the answer to car corrosion problems, but you must remember that it only protects until the coating is 'used up' in the corrosion process, and then normal rusting begins. I think we have all seen very old galvanized roofs and gutters on houses rusting. The coating is used up so there is no longer any protection.
Paints, undercoats and rust proofing treatments are methods of sealing the surface of the steel. They are useful in protecting new steel or steel that has been properly prepared. The problems with seal protection come from adhesion and chipping or cracking of the surface. Porosity of the coating can also be a problem sometimes. Also the protection from any of these coating materials will not function where two parts move or bang against each other. The coating will be quickly worn through if the parts move. Adhesion is the big problem with these types of seals. While they do work very well if the steel is new and clean, and they are properly applied, they can promote more rust if allowed to come loose from the steel because they then hold water against the metal. I am sure we have all seen a small chip in the paint turn into a very large rusty spot because the water works back under the paint. This is why a more flexible coating is better for preventing rust. It won't chip. Soft coatings would be the type of compounds most rustproofers use; they stay soft for a long time and won't chip, but there is still the problem of dirt preventing adhesion.
Most rustproofers will not guarantee their job on any used car because they know the enclosed sections are dirty and possibly rusty. There is no way to clean and prepare the metal in these enclosed sections are dirty and possibly rusty. There is no way to clean and prepare the metal in these enclosed sections, so the coating will not stick. If the coating comes loose, it can hold moisture underneath the coating. The action of the moisture will cause the metal to rust faster and more extensively than it would if there had been no rustproofing in the first place.
Now you are probably thinking that there is nothing that will work to prevent rust. You are partially right. Rust is a never-ending battle, and any Citroen enthusiast must work at it constantly. No matter what coatings you use there is one thing that is easy to do and will help a lot, and that is oil. Oil can be sprayed on over any of the coatings mentioned above. It penetrates and will 'creep' to places missed by the spray. If you have a clean piece of sheet steel coated with oil, you can scratch it and it will heal over because the oil creeps. It is self-healing! While oil does not stay on a clean piece of sheet steel very long, it sticks wonderfully to rusty or dirty metal. Because it will not stay on clean smooth steel very well, oiling must be done often to provide protection. It works best where there is a small gap as it will be drawn right in. There has been much discussion as to what type of oil to use. Most definitely do not use used engine oil! Used oil has acids and water in it and should be avoided at all costs.
If you are spraying you will want a thin oil, or a thick oil that has had a thinning agent added. Red Dellinger used automatic transmission fluid. Others use chain saw bar oil because it is very tacky. Some mix regular non-detergent motor oil with penetrating oil. All of these will work fine. Just be sure to use a non-detergent oil, and don't waste your money on synthetics. Synthetic oils have demonstrated their poor corrosion prevention in the past in engines, and should not be used. The type of oil should not be as much of a concern as frequent application. Be sure it does not dry to a hard finish. You want the oil that you use to be self-healing. If thin it will penetrate better, but if thick it may cling better and last a bit longer.
The next question most enthusiasts ask is, "How do I get the oil inside the doors and frame members?" The easiest way is to drill holes and plug them afterwards with rubber caps. The fastest and easiest way to spray the oil is to use an air compressor to atomize the oil and blow it through the frame and doors. It can be sprayed on the bottom of the car, in the fenders and on the door hinge areas. Other enthusiasts have found other ways of doing it. Some make spray wands to force the oil inside body sections. One has even used an old hydraulic pump that is powered by an old starter motor, all powered with Citroen parts, of course.
Oiling should not be thought of as a method of treatment for rust bucket cars only. It should be done to all cars no matter what their condition. Many seem to think that oiling makes a big mess, but it does not. Your cars will only drip oil for a day or so. Remember, any oil that drips off does not good, so there's no need to overdo it. Use clean oil to minimize mess or stains.
This treatment may seem too simple to those of us who think preventing so insidious a problem as rust must be difficult. The treatment does have to be done often, but it is in fact the treatment recommended by both Citroen, Saab, and who knows how many other unibody car manufacturers. Some of them go into great detail about the oil-spraying equipment and oil temperature (oil is thinned by heat).
When spraying your car with oil, you will not need to drill many holes. The holes you need are already in the car if you know where to look and which plugs to pull out. Be sure not to miss filling the suspension stops and bumper brackets with oil.
I am tired of seeing cars that someone painted with some sort of coating or tar, that simply covered up the rust and held water against the steel, making the car rust faster! Thick coatings might have worked fine, and extended the life of our cars if applied when the car was new and thoroughly dry, but all our cars are far too old for this type of treatment. Water gets behind the coating, and the car rusts like crazy. You must be very sure to get the metal completely dry before treating rust. Rust is like a sponge and holds water for a long time. This is why rust tends to 'snowball' on an owner and makes it seem as if it spreads like wildfire - once it starts. Cars should be stored inside for at least three days (and a week is better) before painting or spraying oil.
Although this work does not require a great investment in tools, many enthusiasts are very reluctant to buy the proper tools to do any job. Adequate results are far more difficult to achieve if you do not have the proper tools! The funny part is that the tools for most jobs can be purchased for far less than the cost of having the job done at a garage. Once you have the tools, you are ready if you need to do the job again, or you can sell the tools and recover most of your investment.
“Should Oil Acquaintance Be Forgot”...
|Copyright 1992 Citroen Car Club