Teaching / Thesis

Active protective coatings on Mg alloys

PhD Candidate: Borja Pillado Ríos

In the course of the doctoral thesis, different coatings are being developed for the corrosion protection of the Mg-Al-Zn alloy; AZ31. Mainly three different coatings are studied: Plasma Electrolytic Oxidation (PEO), Layered Doble Hydroxides (LDH) and Sol-Gel coatings.

PEO coating is a ceramic coating formed form the application of current to the material within an electrolyte. The electrolyte contains different ions such as aluminate, phosphate, silicate, etc. During the PEO process the material’s surface becomes magnesium hydroxide with different species from the electrolyte. The layer formed provides a barrier against corrosion, and it surface presents pores that can be filled with corrosion inhibitors. These corrosion inhibitors are chemical species, that would stop the corrosion in case it get started.

Secondly, LDH coatings are formed via chemical reaction between solved ions and magnesium surface. This reaction can be performed in different way, e.g. hydrothermal reaction, ligands and direct precipitation. The hydroxides formed presents a non-neutral electrical balance that helps to introduce different species between them. These species can be corrosion inhibitors or corrosion agents absorbed form the environment.

Lastly, the Sol-Gel coatings studied are formed from organic and inorganics species. This type of coatings allows the easy incorporation of inhibitors and nanocontainers such as nanoparticles and nanotubes. These can be loaded with inhibitors species. The coatings develop during this thesis will be useful for the corrosion protection of future manufactured alloys.