Monolayered versus multilayered electroless NiP coatings : Impact of the plating approach on the microstructure, mechanical and corrosion properties of the coatings
Salicio-Paz, A. (CIDETEC)
Grande, H. (CIDETEC)
Pellicer Vilà, Eva Maria (Universitat Autònoma de Barcelona. Departament de Física)
Sort Viñas, Jordi (Universitat Autònoma de Barcelona. Departament de Física)
Fornell Beringues, Jordina (Universitat Autònoma de Barcelona. Departament de Física)
Offoiach, R. (Università degli Studi di Udine. Dipartimento Politecnico di Ingegneria e Architettura (Italy))
Lekka, M. (Università degli Studi di Udine. Dipartimento Politecnico di Ingegneria e Architettura (Italy))
García-Lecina, Eva (CIDETEC)

Date:	2019
Abstract:	Electroless nickel-phosphorous (NiP) coatings were produced on low carbon steel substrates for a total plating time of 3 h. Different preparation modalities were pursued. Multilayered coatings were produced by stacking three layers of the same composition by successive electroless plating with rinsing steps in between. On the other hand, coatings termed 'monolayered' for the sake of comparison were deposited by one step electroless process, with and without undergoing bath replenishment of the electrolyte during plating. All the samples were subjected to thermal annealing at 400 °C for 1 h under argon atmosphere. The results show that the multilayer approach prevents crack propagation in the as-deposited coatings because the interfaces between layers block the advance of defects. Bath replenishment during monolayered coatings production creates pseudo-interfaces similar to those of the multilayered case but they are ineffective in terms of corrosion protection. Un-replenishment of the electrolyte promotes a change in the coating's microstructure from lamellar to columnar which severely worsens their performance. Upon annealing, the presence of interfaces, along with the recrystallization of the metallic matrix, promotes an upgrading of the corrosion performance of the multi-layered coatings. The corrosion products spread laterally at the interface where they stockpile. At a certain point, the accumulation of these by-products provokes the exfoliation of the outermost layer exposing the layer underneath to the corrosive media, thereby delaying the advancement of the corrosion attack. The results of this study highlight the importance of the plating approach selection, as well as the need for proper electrolyte maintenance during the production of high-performance electroless coatings.
Grants:	Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-292 Ministerio de Ciencia e Innovación MAT2017-86357-C3-2-R Ministerio de Ciencia e Innovación MAT2017-86357-C3-1-R
Note:	Altres ajuts: MP1407 (COST action e-MINDS)
Note:	Altres ajuts: Departamento de Desarrollo Económico y Competitividad of the Basque Government (ELKARTEK, KK-2017/00096, KK-2018/00108)
Rights:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Language:	Anglès
Document:	Article ; recerca ; Versió publicada
Subject:	Electroless nickel plating ; Multilayers ; Corrosion resistance ; Interface ; Annealing
Published in:	Surface and coatings technology, Vol. 368 (June 2019) , p. 138-146, ISSN 0257-8972

DOI: 10.1016/j.surfcoat.2019.04.013

9 p, 2.2 MB

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