SAARBRUCKEN, Germany - Large quantities of steel are used in architecture, bridge construction and shipbuilding. Structures of this type are intended to be long lasting. Even in the course of many years, they must not lose any of their qualities of strength and safety. For this reason, the steel plates and girders must have extensive and durable protection against corrosion. In particular, the steel is attacked by oxygen in the air, water vapor and salts. Various techniques are used to prevent the corrosive substances from penetrating into the material. One common method is to create an anti-corrosion coating by applying layers of zinc-phosphate. Now, research scientists at INM – Leibniz Institute for New Materials developed a special type of zinc-phosphate nanoparticle. In contrast to conventional, spheroidal zinc-phosphate nanoparticles, the new nanoparticles are flake-like. They are 10 times as long as they are thick. As a result of this anisotropy, the penetration of gas molecules into the metal is slowed down.
“In first test coatings, we were able to demonstrate that the flake-type nanoparticles are deposited in layers on top of each other thus creating a wall-like structure,” explained Carsten Becker-Willinger, Head of Nanomers® at INM. “This means that the penetration of gas molecules through the protective coating is longer because they have to find their way through the cracks in the wall.” The result, he said, was that the corrosion process was much slower than with coatings with spheroidal nanoparticles where the gas molecules can find their way through the protective coating to the metal much more quickly.