How to protect steel from rust?

Steel is a very universal material that high stability and adaptability captivates. Steel components, like bridges, railing or resound make favorable, easy and quick to erect. However, steel has a known weak point – rust.

If steel is left unprotected and exposed to the effects of the weather, rusty spots can be seen after a short time. To counteract this, steel always needs a suitable one rustproofing. To understand how to protect steel from rust, let's first look at how rust occurs in the first place.

How is rust formed?

Rust occurs when the iron in the steel reacts with the oxygen in the air. It arises from this Iron oxide, also known colloquially as rust. Humidity and Sugar and salt speed up this process. That is why rust protection is all the more important near the sea. 

Initially, the rust is just a visual problem, but as the corrosion progresses, the components weaken. The tube of a balcony railing then becomes thinner and thinner and could eventually buckle under load. 

Das ist ein security risk and must not happen. Therefore, there are many ways to protect steel structures from rust.

Protection against rust by painting

There are different methods to protect steel from rust. This is a very simple and cheap method paint. Painting becomes the steel covered with a layer of paint, which means that the iron can no longer react with the oxygen in the air. This corrosion protection remains in place as long as the Paint layer intact and free of cracks is. After some time, the paint layer should be renewed to prolong the protective effect. are problematic cavities, because it is difficult or impossible to paint there. So there is no corrosion protection there. At least these areas are usually protected from moisture, so that oxidation progresses more slowly. However, one should always try to preserve the cavities as well. If painting is not possible, you can too cavity Protection use.

Rust protection by powder coating

Powder coating has a similar effect to painting. Here, however, the paint is not applied with a brush or a spray head, but with a special system. In a powder coating plant becomes a colored powder electrostatic charged and then adheres to the workpiece. The component is then heated, causing the powder to bond with the surface to form a continuous layer of paint.

Protection against rust by galvanizing

When galvanizing, the zinc layer protects not only by enclosing the steel, but also by a cathodic protection against corrosion. This means an additional protection, which results from the different electrical potential of zinc layer and steel. Instead of reacting with the steel, the oxygen first reacts with the zinc layer until it is consumed. It is working even with minor damage such as scratches, cuts or holes.

There are various methods for applying the zinc layer. Hot-dip galvanizing is usually chosen for railings or larger steel beams. The components are immersed in molten zinc. Another advantage of galvanizing is that the components also inside be coated. However, holes must be drilled so that the air can escape and the zinc can drain off. 

More about galvanizing processes and costs.

Stainless steels

There are also steels that do not rust. At least not under normal conditions. 

These steels are made by adding the alloying elements chrome and nickel refined. 

Depending on the proportion of alloying elements, there are different types of stainless steel, eg V2A or V4A. In industry, other designations such as 304/316 or 1.4301 are usually used. 

It is important to know that these steels can also rust under certain conditions. Influencing factors are, for example, salt (sea), humidity, temperature or chemicals. As a rule, the higher the requirements, the higher the proportion of alloying elements. Nickel is very expensive, which is why stainless steel significantly is more expensive than normal steel.

What is the cheapest way to protect steel from corrosion?

Painting or hot-dip galvanizing is usually the cheapest. The cost difference for new components is not very large and also depends on the component geometry. In the case of existing steel constructions, painting is usually cheaper because the components do not have to be completely dismantled and transported. Stainless steel is significantly more expensive and is therefore usually only used for aesthetic reasons, e.g. for railings, or in the process industry.

Which corrosion protection lasts the longest?

Stainless steel remains protected against corrosion for the longest time. Galvanized components are also resistant to rust for a very long time. If these are also deleted, the protection period is extended enormously. Painted components should be repainted after a few years if they are directly outdoors.