Improvement of the Corrosion Resistance
Entrapment of Hard Particles into Cr(VI)-Free Conversion Layers
Due to the restriction of passive layers containing Cr6+ [1], which were characterized by excellent corrosion protection due to their self-healing effect for scratches on metal surfaces, current corrosion protection systems consist of chromium (III) -containing thick layer passivation. Due to their lower hardness, current corrosion protection systems are susceptible to mechanical stress. This is particularly critical at barrel plating of screws, rivets etc. where the manufacturing process leads to damages of the corrosion protection layer and consequently to reduced corrosion resistance.
To counter this problem, we point out one approach to install hard particles into the passivation layer. The entrapment of the hard particles into the passivation is detected by Glow Discharge Optical Emission Spectrometry. Comparative investigations in the corrosion chamber prove the improvement of the corrosion protection of steel parts with passivation layers containing hard particles [2,3].
References
[1] Anhang II der Richtlinie 2000/53/EG des Europäischen Parlaments und des Rates über Altfahrzeuge, C (2002) 2238.
[2] Jehl, P., Halbedel, B., Lerp, M., Schmidt, U., Teichert, G., Schlütter, F.: Entrapment of Hard Particles into Cr(VI)-Free Conversion Layers of Electrodeposited Zinc Coatings to Improve Corrosion Resistance. Key Engineering Materials “21st Symposium on Composites”, Volume 742, pp 434-439, 2017, doi: 10.4028/www.scientific.net/KEM.742.434
[3] Halbedel, B.; Schmidt, U.; Lerp, M.; Jehl, P.; Camargo, M. Teichert, G.; Wilke, M.: Beschichtung eines eisenhaltigen Werkstoffes und Verfahrens zu deren Erzeugung sowie Werkstück. DE 10 2017 103 602.4, angemeldet: 22.02.2017
