Alternatives to galvanizing and powder coating

For buildings and building parts made of steel, such as balconies, railings or carports, the surface coating of the components plays an important role. On the one hand, it should set visual accents and, on the other hand, protect the components from environmental influences and corrosion for as long as possible. There are mainly three types of surface finishing in steel construction with structural steel:

• paint
• Galvanizing
• powder coating

Painting and powder coating provide corrosion protection by keeping oxygen away from the component surface. For galvanized components, corrosion protection is additionally achieved through electrochemical protection, which also works on defects such as surface cracks. Details can be found in this Articles about galvanizing.

Better corrosion protection through a combination of processes

If you want to design the components in color and still not forego the cathodic corrosion protection of galvanizing, the processes can be combined by first galvanizing the components and then coating them with wet or powder paint.

This gives you double corrosion protection that resists strong environmental influences.

Disadvantages of galvanizing and coating

The combination of the methods not only has advantages, but also has disadvantages:

Extensive preparation

Galvanized components cannot be coated directly. Galvanizing can cause rough spots, pimples or flaking of the zinc layer. These areas must be laboriously cleaned and reworked.

dimensional accuracy

When galvanizing, the components are immersed in a bath of liquid zinc. The surface that is created is not the same thickness everywhere. Thickenings occur in places where the zinc cannot drain away easily; in other places the zinc layer can be thinner.

Component geometry

For hot-dip galvanizing, the components must be designed in such a way that the liquid zinc can reach all parts of the component and also flow away again. Where this is not possible, appropriate drilling must be provided. Depending on the intended use, these holes can be perceived as annoying.

Costs

The additional costs for galvanizing are around €0,40/kg. There are also transport costs and costs for preparing the zinc layer for coating. Typically, the combination of galvanizing and coating is more than twice as expensive as coating alone.

Higher corrosion resistance without galvanizing

A few years ago, the Max Planck Society developed an alternative to galvanizing and coating. Based on the self-healing powers of human skin, a coating was developed that independently repairs defects. For this purpose, so-called “smart pigments” are incorporated into the coating. In the event of defects or cracks, these tiny containers release an anti-corrosion agent that closes the surface again.

Last revised on April 22, 2021 by Andreas Janisch