title: Sealing of hard CrN and DLC coatings with atomic layer deposition.
abstract: Atomic layer deposition (ALD) is a thin film deposition technique that is based on alternating and saturating surface reactions of two or more gaseous precursors. The excellent conformality of ALD thin films can be exploited for sealing defects in coatings made by other techniques. Here the corrosion protection properties of hard CrN and diamond-like carbon (DLC) coatings on low alloy steel were improved by ALD sealing with 50 nm thick layers consisting of Al2O3 and Ta2O5 nanolaminates or mixtures. In cross sectional images the ALD layers were found to follow the surface morphology of the CrN coatings uniformly. Furthermore, ALD growth into the pinholes of the CrN coating was verified. In electrochemical measurements the ALD sealing was found to decrease the current density of the CrN coated steel by over 2 orders of magnitude. The neutral salt spray (NSS) durability was also improved: on the best samples the appearance of corrosion spots was delayed from 2 to 168 h. On DLC coatings the adhesion of the ALD sealing layers was weaker, but still clear improvement in NSS durability was achieved indicating sealing of the pinholes.
authors.affiliation: Laboratory of Inorganic Chemistry, University of Helsinki , P.O. Box 55, FIN-00014 Helsinki, Finland.
authors.forename: Emma
authors.initials: E
authors.lastname: Härkönen
authors.forename: Ivan
authors.initials: I
authors.lastname: Kolev
authors.forename: Belén
authors.initials: B
authors.lastname: Díaz
authors.forename: Jolanta
authors.initials: J
authors.lastname: Swiatowska
authors.forename: Vincent
authors.initials: V
authors.lastname: Maurice
authors.forename: Antoine
authors.initials: A
authors.lastname: Seyeux
authors.forename: Philippe
authors.initials: P
authors.lastname: Marcus
authors.forename: Martin
authors.initials: M
authors.lastname: Fenker
authors.forename: Lajos
authors.initials: L
authors.lastname: Toth
authors.forename: György
authors.initials: G
authors.lastname: Radnoczi
authors.forename: Marko
authors.initials: M
authors.lastname: Vehkamäki
authors.forename: Mikko
authors.initials: M
authors.lastname: Ritala