To prevent corrosive substances from penetrating into materials, a common method is to create an anti-corrosion coating by applying paint layers of zinc-phosphate particles. Now, research scientists at INM developed a special type of zinc-phosphate particles: They are flake-like in shape because they are ten times as long as they are thick.
First experiments with those new, flake-type shaped particles indicate, because of their anisotropy, a better solubility compared to spherical particles. Now, more phosphate-ions are soluted and repassivation of bare metal surface, for example as a consequence of a mechanical damage, is better and faster.
In first test coatings, the scientists were able to demonstrate that the flake-type particles are deposited in layers on top of each other thus creating a wall-like structure. 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 was, that the corrosion process was much slower than with coatings with spheroidal particles where the gas molecules can find their way through the protective coating to the metal much more quickly.
In further series of tests, the scientists were able to validate the effectiveness of the new particles. To do so, they immersed steel plates both in electrolyte solutions with spheroidal zinc-phosphate particles and with flake-type zinc-phosphate particles in each case. After just a few hours, the steel plates in the electrolytes with spheroidal particles were showing signs of corrosion whereas the steel plates in the electrolytes with flake-type particles were still in perfect condition, even after three days.