Improved Corrosion Resistance of CrN Hard Coatings with an ALD Al2O3 Interlayer

As mentioned in the previous post  - Han-Bo-Ram Lee research group at the Nanomaterials Laboratory of  Incheon National University Korea has a nice blog/news service where they publish all recent results on regular basis.

http://nanomaterial.kr/

Here I found this paper on using ALD interlayers for CrN corrosion protection coatings

[Paper]Improved Corrosion Resistance and Mechanical Properties of CrN Hard Coatings with an Atomic Layer Deposited Al2O3 Interlayer

Zhixin Wan, Teng Fei Zhang, Han-Bo-Ram Lee, Ji Hoon Yang, Woo Chang Choi, Byungchan Han, Kwang Ho Kim,and Se-Hun Kwon

ACS Appl. Mater. Interfaces, Article ASAP
DOI: http://pubs.acs.org/doi/pdf/10.1021/acsami.5b08696

Abstract

A new approach was adopted to improve the corrosion resistance of CrN hard coatings by inserting a Al2O3 layer through atomic layer deposition. The influence of the addition of a Al2O3 interlayer, its thickness, and the position of its insertion on the microstructure, surface roughness, corrosion behavior, and mechanical properties of the coatings was investigated. The results indicated that addition of a dense atomic layer deposited Al2O3 interlayer led to a significant decrease in the average grain size and surface roughness and to greatly improved corrosion resistance and corrosion durability of CrN coatings while maintaining their mechanical properties. Increasing the thickness of the Al2O3 interlayer and altering its insertion position so that it was near the surface of the coating also resulted in superior performance of the coating. The mechanism of this effect can be explained by the dense Al2O3 interlayer acting as a good sealing layer that inhibits charge transfer, diffusion of corrosive substances, and dislocation motion.