FE2O3 - Rust, Tinworm, Red Rot.

By Don James

From the CCC Newsletter, Hollywood, USA. This article appeared in the CCCV Newsletter in July and August 1992.

Part 1 Causes and where to look Part 2 Probing for rust and treatments Home

rusted D hulk in desert

Probably the biggest factor that effects the life of your Citroen,no matter what model you own, is rust. Because of the way the chassis of these cars is constructed, even a small amount of rust can cause terrific weakening of the structure. The chassis gets its strength from thin sheet steel that is bent into shapes to gain strength. Many of these shapes are enclosed box-sections that make internal rusting impossible to see. To really understand the problems involved in preventing rust, we must go back to the time the car was made. The manufacturer is faced with the problem of fastening, bending, and welding bare sheets of metal as it comes from the roll, yet it must still look good on the outside so the car is easy to sell. The steel as it comes from the roll is covered with oil. Parts that come from a stamping die are covered with oil which is used to lubricate the stamping operation. These parts must then be cleaned to prepare them for welding or painting. This must be done rapidly in order to keep production rolling. The best surface for painting is one that is sandblasted. Sandblasting will also warp thin sheet steel, so this method is out of the question for the manufacturer.

Most auto manufacturers use a method of acid etching called pickling to clean and prepare the metal for paint. The acid will etch and clean the metal quickly, and will not warp or distort the part. It can be used on welded assemblies, but there is a problem of the acid getting into and especially out of the spot welded joints.

Spot welded areas must be clean and free of paint. Even galvanizing causes problems. The problem with keeping enclosed joints rust-free is that they can only be sealed from somewhere away from the joint, where the sheets of metal are spread far enough apart to be coated with any sort of compound that will seal it. Like most manufacturers, Citroen dips their chassis in paint.

When the D and SM models were made, they used a fast-drying paint to speed production after the paint dip. This did not allow much time for the paint to penetrate into the seams and joints. Now that they have computer-controlled transfer lines, they do not have to allow the paint to dry on-line. The chassis are dipped into a paint which is slower drying and more penetrating. The parts are then conveyed to a storage area where the paint dries, and returned to the live production line. It is too bad they did not have such methods when they built the DS and SM models.

The same methods that the manufacturer used can be simulated by the owner if he is willing to spend some time replacing rusted or bent sheet metal. The repair of rust on your Citroen is not very difficult, but it does take a lot of time. Since 'time is money', it usually costs a small fortune to take your car to a shop to have the rust repaired professionally. A good body shop does have special tools that cut down on the time required. If the rust damage is extensive it may not be worth fixing the car from a strictly practical standpoint.

If you have a fairly nice car, prevention of rust is much easier. The best way to prevent rust on your car is to study other Citroens that have rusted to see what areas typically require attention. Citroens do not show rust easily, so if you see any rust on the outside of your car's bodywork, it is sure to have much more damage where you can't see it.

Since you have probably ignored the elements of rust prevention until the first spot appears, you should feel justifiably foolish in having ignored the possibility. This does not mean that your car is now doomed to imminent collapse. The decision to cure the rust rather than return to the world of car payments and more mundane (non-Citroen) transportation is yours alone.

There is no such thing as a rust-free Citroen, since surface rust on uncoated parts comes straight from the factory. The rust condition is just a question of degree. An exhaustive list of the areas where these cars can rust would be too extensive. A list of areas where rust is rarely found would be much shorter. The major areas that need attention are:

  1. Just above the front fender wheel well opening on the inside of the fender. Also at the mounting bracket that is attached to the inside of the fender well. This is spot-welded on, and because it is in the fender well, it collects mud and dirt. This holds the water and before long, you will have a hole in your fender that will allow your wheel to throw on the back of your headlights. The turning headlights in the late D's will collapse if this area and its struts disappear. The dogleg at the very bottom of the front fender behind the front wheel is also an important place to check.
  2. Doors rust out at the very bottom edge where the outer skin is folded over the bottom of the door. This is a terrible place for a seam because it is at the low point of the door. If your car is not rusty here, it is probably in pretty good shape elsewhere. Be sure the door's drain holes are open! They may be clogged with leaves or dirt. If the car was ever rust-proofed in the past, these drain holes are probably clogged with rust-proofing when it was put on, or sagging over the holes later in the summer heat. Remember, drain holes are the most important means of preventing rust. They must not be allowed to remain clogged. The only caution is that they must not be so big as to let in mud and water. If your window seal does not seal completely, the water will run down the inside the door and rust the retaining strip that holds the seal to the inside of the door. You must remove the rubber the check this. The front door has one problem area not affecting the rear door. Down in the door hinge area there is a rubber sealing flap. Water from the windshield drains down here and causes a pocket of moisture at the very front on the inside of the hinge area.

  3. A leaking roof or window will allow water to drain into the floor pans. Getting into the car with wet feet can fill the foam carpet backing with water. Everyone loves the thick foam carpet padding on these cars, but the foam does tend to hold water for a very long time. Dirt and leaves under the carpet also hold water. Remove the carpets and thoroughly clean the floor pans, noting the condition of the corners and the Pallas soundproofing pads. Pay particular attention to the area under the pedals. This triangular box section of the frame is also inclined to rust.

    The first line of defense is the lid-to-window seal. If this is properly positioned, water will drain around the fender channels, leaving the inner seals dry. The thin rubber flaps that seal the inner portion of the trunk lids of the early cars have been replaced by the thick foam. Any tear in the rubber skin of these foam seals allow water into the foam, promoting rust on the lid and the trunk rim in a hurry. Small tears in the skin of this seal can be repaired with black silicone rubber. Silicone spray would then provide some ice-release protection, as this seal gets torn when the trunk is opened, taking some of the skin with it.

    No discussion of trunk rust would be complete without mentioning the jute backing on the vinyl trunk lining. The jute will absorb water and the vinyl will keep it from evaporating. It effectively holds water against the trunk walls and floor. Remove the panels and let them dry thoroughly. Any attempt to seal the panel edges will only trap moisture permanently when it enters unannounced. Be sure to pull the edging from the rolled edges of the trunk rim. These will show rust that is in the structural joint between the fender supports and the trunk walls.

  4. Roof leaks will drain into the small trough around the inside the roof. It will pour down to the trunk or package shelf unless you park downhill, then it will fill your front seats. If you have a Pallas model, you must stick your finger between the headliner and the padded embellishment in order to feel this trough. Check this area after a hard rain for signs of moisture. If your finger gets wet, you have a roof leak. You will probably already have noticed stains creeping up from the edges of the headliner. The official method is to remove the roof trim from the outside of the car and fit a new gasket and sealer to the roof Although very effective, this is virtually never done due to the difficulty and the chance of creating new leaks due to lack of experience - not many people seal roofs more than once.

    To fix the roof leak, first remove the roof trim from the outside of the car and the trough trim from the inside of the car. Loosen the bolts holding the roof down, which may be found all along inside the channel. Liquid Wrench (or something similar) will probably be necessary to free some of them since they have been wet. From the outside, pry the rubber away from the roof and the outside channel a small amount. Use a small screwdriver and follow along with a vacuum to remove the dirt, rust and foreign matter. Next, clean this groove with solvent, checking first to see that it won't damage the paint on the roof. Squirt Penetrol [a penetrating sealant] along the gasket, inside and out. In a few days it will have penetrated everywhere the water could go and it will dry, providing a perfect base for a sealant.

    A caulking gun with Geocel [or a good quality black polyurethane sealant] will finish the job. Geocel is like silicone sealant, but is much tougher and more rubbery. Wipe the excess sealant off with a rag and then immediately tighten all the bolts that hold the roof onto the car. Replace the inner and outer trim, and you're done.

  5. Trunk leaks are one of the worst things that can give problems. Because the trunk slopes to the front of the car, any water from spills or leakage will run forward under the cover that hides the anti-roll bar. Water will lay there hidden view and rust the floor and chassis.

  6. The gas tank filler tube is, aside from the bottom of the doors, the worst design defect in terms of rust. This tube slopes toward the gas tank, conducting water from the fender well right into the gas tank box. This causes all kinds of rust in the box and along the side rails where the owner can never see it. Usually the most damage is beneath the gas tank where you cannot see it even if you open the cover to the gas tank box. Often the gas tank rusts out or is rusted around the filler tube, causing fumes and leakage from the tank. Prevention of this problem is easy. The area where the filler tube goes into the gas tank box must be sealed so that water cannot follow it into the box. This should be the first priority for any owner!

As you can see, fighting rust is just common sense. It takes time, and you have to look for it. It would be impossible to cover all the rust points, but careful examination of less fortunate cars can help you out. Remember that covers and sound-deadening material usually hide rust. Even the area inside the rear turn signals on your late-model D gets rusty. You can't see it until it is too late. Did you ever try to remove the lens and socket? It is almost a sure bet that it is rusted inside.

In our next part, we will cover the methods used to probe for this rust and how to protect and paint the metal. We will also try to cover the different methods of replacing rusty metal.

Copyright 1992 Citroen Car Club