Rust is perhaps the classic car owner's biggest nightmare. Okay, totaling a car and theft might rank just a little higher, but the rust devil can wreak enormous damage on your classic vehicle. Rust is nothing more than oxidized iron, we were always told in chemistry. This iron combines with oxygen, and then you have a real rust problem. Models like the Alfa Romeo 33, Ford Fiesta and the Opel Corsa were notorious for their susceptibility to rust. But there is a bit more to tell about this merciless process. What exactly is rust, and how does it work?

First of all, we are not talking about iron, but about steel, which is composed of multiple metals. During the production of steel, scrap is also melted and mixed in. This scrap consists of all kinds of metal residues, such as aluminum and copper from, for example, car wrecks. These metals all behave differently and contain small voltage differences, also known as potential differences mentioned. This is where it gets tricky, because if a conductive substance, such as rainwater, causes contact between the different types of metal crystals, a tiny electric current is generated, which causes the least noble metal to slowly begin to dissolve.

Moisture is everywhere, even if you don't see or feel it.

Even if a metal does not feel wet, there is always a very thin layer of water present on the surface due to the humidity around us. This thin film of water is electrically conductive, especially with some road salt or other dirt swirling around in it. We therefore have impure steel consisting of multiple metals, coupled with a thin film of water containing impurities. Both cause minute potential differences and, consequently, small electrical currents. On the negative side, we have the least noble metal (often iron) dissolving, and on the positive side, we have water that splits.

The released hydroxide ions are negatively charged and subsequently bind with the positively charged iron ions to form iron hydroxide. This becomes visible to the eye as a reddish-brown substance, and as the process progresses, it changes into reddish-brown flakes of iron oxide, which we encounter as an unpleasant surprise on our beloved classic cars. An additional drawback is that rust always contains water, and just one molecule of water is sufficient to ensure that the rusting process continues.

One way to truly halt rusting is by electrifying the metal. This prevents the formation of iron ions. However, continuously electrifying your classic car isn't exactly a solution. What is interesting is 'cathodic protection,' which is achieved by applying a thin layer of zinc. Zinc is actually even 'less noble' than iron, meaning electrons are more likely to escape from the latter during the rusting process. Therefore, instead of iron dissolving, the zinc dissolves. The end product of zinc corrosion is 'zinc patina,' which is rock-hard and forms a sealing layer. In this way, the rusting process comes to a standstill because the zinc corrodes, rather than the metal we want to protect.

When recycling galvanized steel, it is important that the steel is free of zinc. For example, engine blocks cannot be cast from steel containing zinc because this can form bubbles, compromising the block's strength. Fortunately, zinc evaporates well before the processing temperature in the steelmaking furnace and is captured in a separate vapor process; zinc oxides are recovered from this residue. These zinc oxides are then used in medicines, dietary supplements, skincare, makeup, etc.

In earlier times, much technology was less developed, and we were also less environmentally conscious. Removing zinc oxides from the process was costly due to the extra equipment required. Furthermore, there was no demand for zinc oxides; they were simply extracted from the primary zinc in zinc ore. Nowadays, people realize that we are depleting the earth's resources. For this reason, reuse is highly necessary, and recycling companies, processes, and markets have really taken off.

A common attempt is to control the rust: sanding it away a little and repainting. However, this does not help, because under the new paint the rust simply continues to spread, and eventually you will see blisters forming in the paint that will eventually burst open like ripe cherries. The consequence of this is that moisture can penetrate even more easily, accelerating the process. If you really want to get rid of the rust, you will have to take very rigorous measures. You can do this by removing the rusted section or by very thoroughly derusting it using sandblasting. It is important that you apply a covering and completely sealing coat of paint as soon as possible after sandblasting, because if the metal is exposed to the open air, it will start to rust again.

Rust caused by bacteria

Even with brand-new, well-prepared metals that are completely sealed off from oxygen with multiple layers of coating, rust can still occur. This is due to bacteria that settle in the metal. These bacteria secrete minute amounts of moisture that are sufficient to cause rust to eat its way out from the inside.

This all sounds quite hopeless for a winning battle against rust. Is it a done deal from the start, then, and must we accept that sooner or later every classic car will fall prey to rust?

How to deal with rust?

When you want to protect a car against rust as effectively as possible, it is important to start with a clean and dry car. So, begin by cleaning with the right products and removing all cover plates and protective caps. Be sure not to forget the hollow spaces. These types of spots often contain dirt where rust is already lurking. Every nook and cranny you forget increases the risk of rust, so tackle this very thoroughly and ensure you can reach everywhere properly with a pressure washer. Then, let the car dry thoroughly; this takes about 48 hours, so allow that time.

Next, there are countless products from various brands that you can use. We will not advise on these for the simple reason that we do not really know what works and what doesn't. What is known, however, is that grease-based products (not wax) deliver the best results. There are many products on the market that do not get the job done, or do so inadequately. Therefore, seek advice from specialists regarding this. If anyone has a good independent test, we would be grateful to hear about it. In any case, it is wise to ensure that you inspect your classic car regularly, keep it in a dry and ventilated environment, and try to avoid influences that can contribute to rust (think of winter conditions).

Happy driving!

Thanks to Hans Boender for his contribution to this article.