- https://www.cells.es/ca/actualitat/agenda/esdeveniments-publics-dalba/decorative-chromium-coatings-on-the-automotive-sector
- Decorative chromium coatings on the automotive sector
- 2019-12-10T15:00:00+01:00
- 2019-12-10T16:00:00+01:00
- Jesús Manuel Vega and Jonathan León from CIDETEC (Bask Country)
- Què
- events
- Quan
-
Des 10, 2019
de 15:00 a 16:00 (Europe/Madrid / UTC100) - On
- ALBA Synchrotron, Marie Curie Meeting Room
- Nom de contacte
- Manuel Valvidares
- Telèfon de contacte
- 935924484
- URL de l'esdeveniment
- Lloc web relacionat
- Afegeix un esdeveniment al calendari
-
iCal
The so-called decorative chromium coating (100-300 nm thickness) has been widely used in several industrial sectors due to its aesthetic appearance and good corrosion resistance performance. Traditionally, these coatings are usually made up of multilayer system: a top microporous chromium layer plated over three distinct nickel layers (microporous nickel, bright nickel and semibright nickel, from top to bottom). Cr(VI) based electroplating baths have been used to obtain such coatings; however, the use of this compound was strictly limited by the REACH (Registration, Evaluation, Authorisation and Restriction of Chemical Substances of the European Union) because it has a harmful impact due to its toxicity and carcinogenic effects. Since then, the development of new environment-friendly coatings has been promoted, being Cr(III) based electroplating baths one of the main alternatives.
This talk has been divided in two blocks: the first one will address the features of a multilayer chromium-nickel system (complete commercial system) focused on its corrosion resistance. Typically, an accelerated corrosion test called CASS (Copper Accelerated acetic acid Salt Spray) has been used for evaluating the resistance of the coatings in the automotive industry. However, the visual evaluation of the corrosion using CASS test does not provide enough information about the degradation mechanism behind it and the impact of the CASS electrolyte on the coating performance. Therefore, a rigorous and quantitative approach using conventional and localized electrochemical techniques has been used to explore the corrosion mechanism. It has been found that the presence of cupric cations in the electrolyte has a drastic impact on it.
Secondly, the chromium layer has been isolated from the multilayer system in order to carry out a tailored characterization using Cr electrodeposits obtained by different Cr(III) based electroplating baths (model and commercial ones). In general, such coatings do not present the same properties than Cr(VI) based ones and it is known an effect to the corrosion resistance depending on the type of coating. This might be due to the differences in the physical-chemical properties of the native oxide layer and the metallic Cr coating underneath. A different chemical composition has been obtained in the Cr coatings and their oxides (i.e. presence/type of carbides and iron) that affects to the corrosion resistance and semiconducting properties of their native oxide layer.
