Initiation and growth of modified Zr-based conversion coatings on multi-metal surfaces

Cerezo, José María Palencia; Vandendael, Isabelle; Posner, R.; Lill, K. A.; Wit, J.H.W. de; Mol, J.M.C.; Terryn, Herman

doi:10.1016/j.surfcoat.2013.09.059

Cited by 92 publications

(84 citation statements)

References 37 publications

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“…The coating formation process for Zr or Ti coatings involves activation of the surface in the acidic fluoride-containing bath and subsequent deposition of the coating. The deposition mechanism has been studied using open circuit potential (OCP) vs. time curves, 6,58,85,87,92,102 mass change, 6 Scanning Kelvin Probe (SKP) maps, 34,55,103 compositional analysis by Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS), 34 Rutherford backscattered spectroscopy (RBS), 49 glow discharge optical emission spectroscopy (GDOES) 49,104 and time-of-flight secondary ion mass spectroscopy (ToF-SIMS), morphological analysis 51,71,88,[93][94][95][96]103,105 and local pH measurements. 92,106 Aluminum parts are usually pretreated by alkaline etching and acid de-oxidizing.…”

Section: Deposition Mechanismmentioning

confidence: 99%

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Review—Conversion Coatings Based on Zirconium and/or Titanium

Milošev

Frankel

2018

J. Electrochem. Soc.

148

113

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There is a growing interest in conversion coatings based on titanium and/or zirconium as the result of the health and environmental issues associated with legacy chromate and phosphate conversion coatings. Any alternative technology should be environmentally friendly and cost effective, and also able to achieve comparable corrosion resistance and paint adhesion for ferrous and non-ferrous substrates. Conversion coatings based on titanium or zirconium seem to fulfill many of these requirements and thus offer a great potential for further applications. This literature review summarizes the scientific results in this rapidly growing area of research. Following the description of composition of conversion bath and deposition mechanism, the effects of process parameters for conversion baths such as pH, temperature, immersion time and agitation are presented together with coating characteristics. The effects of the type of substrate and substrate pre-treatment are explored for the most-studied substrates: Al alloys, zinc-coated steels and steels. Properties such as composition, morphology and thickness are summarized. The corrosion performance of the conversion coatings is discussed, as well as adhesion of organic coatings and delamination mechanism for a full coating system including substrate/coating/top-coat. Metals used in the construction of products and facilities in most applications, including industrial, infrastructure, transportation, construction, consumer goods, etc., are primarily selected from three groups: steels, zinc-coated (galvanized) steels, and aluminum alloys (AA).1 All of these materials require protection to prevent environmental degradation, and the most common approach to protection against corrosion is a multilayer coating system. Metal components are treated by a series of processes to create this coating system: cleaning, surface pre-treatment, and application of organic coating layers including primer and topcoat. Surface pre-treatments include anodizing (for aluminum alloys) and conversion coatings, which are the focus of this review. Conversion coatings are formed by immersion of a component in a chemical bath and reaction of the metal substrate with the components in the bath to form a layer that coats the surface. These layers provide some corrosion protection by acting as a barrier to the environment or releasing corrosion-inhibiting species. However, their primary role is to improve the adhesion of subsequently applied paint layers.The most important conversion coatings used for corrosion protection and adhesion promotion of ferrous and non-ferrous metal substrates are chromate conversion coatings (CCCs) and phosphate coatings. CCCs are highly corrosion protective. They consist of a backbone of chromium oxide/hydroxide with Cr in the 3+ oxidation state and also contain compounds with Cr in the 6+ oxidation state. 2-5The Cr(VI) provides the characteristic of self-healing, which is the ability to reform a protective coating after it has been breached by a mechanical or chemical proces...

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Section: Deposition Mechanismmentioning

confidence: 99%

“…102 The difference between the initial potential and the minimum potential varies for different substrates and is the greatest for Al-based and smallest for steel substrates. 85 ) unless CC License in place (see abstract The reactions of oxygen reduction and hydrogen evolution take place at cathodic sites:…”

Section: Deposition Mechanismmentioning

confidence: 99%

Review—Conversion Coatings Based on Zirconium and/or Titanium

Milošev

Frankel

2018

J. Electrochem. Soc.

148

113

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“…29 The presence of Cu was shown to be the driving force behind the increase in pH on the substrate which leads to a more homogeneous deposition. 30 Differences have been reported in the Cu distribution between the different substrates steel, zinc, and aluminum alloys, where especially on AA6014 large inhomogenities have been found. 30 So far, the nucleation times and mechanism of the Cu particles present on the surface have not been investigated, which is one of the major motivations for this work.…”

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confidence: 99%

“…30 Differences have been reported in the Cu distribution between the different substrates steel, zinc, and aluminum alloys, where especially on AA6014 large inhomogenities have been found. 30 So far, the nucleation times and mechanism of the Cu particles present on the surface have not been investigated, which is one of the major motivations for this work. As metallic Cu is unlikely to nucleate on a surface that is already covered with ZrO 2 , the competition between Cu deposition and ZrO 2 deposition may lead to z E-mail: a.erbe@mpie.de; aerbe@arcor.de interesting co-localisation phenomena.…”

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confidence: 99%

Role of Intermetallics and Copper in the Deposition of ZrO₂Conversion Coatings on AA6014

Sarfraz

Posner

Lange

et al. 2014

J. Electrochem. Soc.

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Zirconium oxide based conversion coatings are nickel-free alternatives to trication phosphate coatings. Here, the role of intermetallic inclusions in aluminum alloy AA6014 on the formation of Cu-rich particles inside ZrO 2 -based conversion layers with a film thickness of 25-30 nm was investigated. The role of the intermetallic inclusions on the deposition mechanism was characterized by varying the immersion time of the substrate and analyzing the coatings by electron microscopy and atomic force microscopy. Statistical analysis on the growth of the copper rich particles showed instantaneous nucleation of these particles, with a subsequent homogeneous inplane growth at constant height. A strong preferential nucleation of the Cu-rich particles on the intermetallic particles was observed, and was attributed to the cathodic nature of the intermetallics. Raman spectroscopy indicated the presence of crystalline CuO and amorphous ZrO 2 in the film. Enhanced layer formation in the vicinity of intermetallic particles was observed. Conversion coatings are widely used to protect metal surfaces from corrosion and to promote the adhesion of subsequently applied organic paints.1 While phosphate-based conversion coatings still have a large range of applications and some aspects of their formation are subject to more recent work, 2,3 current efforts focus on the replacement of conventional, μm thick phosphate and chromate containing systems by thin coatings that results in layers with an average thickness of just few tens of nm, without toxic ingredients. [4][5][6][7] One class of candidates are rare-earth based coatings. 4,6,[8][9][10] Other candidates are nanoceramic conversion coatings, typically containing zirconium or titanium oxides. Such coatings are either deposited on the surface by sol-gel chemistry, or by immersion into a fluoric acidic of Zr/Ti. Nanoceramic coatings have been shown to provide good multi-metal corrosion protection for various substrates including steel, zinc, and Al alloys, [11][12][13][14][15][16][17] and combine good corrosion performance with excellent adhesion properties. 5,[18][19][20][21][22] A lot of work has been specifically focused on investigation of zirconium or titanium based pretreatment on Al alloys. Their basic film formation mechanism is (i) fluoride etching of the oxide layer (which can be replaced by alkaline treatment), 23 (ii) onset of hydrogen evolution reaction, i.e. water reduction with a consequent increase in pH near the interface, and (iii) subsequent precipitation of oxyhydroxides as oxide precursors.24-27 Inclusion of Cu II salts (or alternatively, Fe salts) in the bath has been shown to lead to higher overall growth rate of the film on cold rolled steel compared to the solutions without Cu II . 25,28 Coatings prepared by including copper in the solution were also shown to be thicker and showed enrichment of copper within the conversion film. 25,28 Painted cold-rolled steel pretreated with a Cu-containing ZrO 2 -based coating shows low frequency impedance moduli comparabl...

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“…There are studies [23,[25][26][27][28] where is shown that nano-Zr coatings are used as pre-treatments for organic paints. However, according to the purpose of this work, the nano-Zr and tannin based colorant can be used without the paint layer, whereas it had a similar corrosion protection to that of Cr III based coatings.…”

Section: Resultsmentioning

confidence: 99%

Corrosion Behavior of a Conversion Coating Based on Zirconium and Colorants on Galvanized Steel by Electrodeposition

Costa¹,

Agnoli²,

Ferreira³

2015

TMM

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Corrosion performance of Zr-based coating on substrates obtained by zinc electrodeposition in an alkaline bath is compared to chromate coatings (Cr III and Cr VI). The "nano Zr" is a conversion coating formed by immersion in a hexafluorozirconic acid solution. Since the "nano Zr" coating is transparent, the addiction of a colorant provides color to the surface. In this case, the colorant, when applied after the conversion coating, conferred the yellow color to the surface. The coating produced improves the corrosion protection of the substrate. For this study the samples were analyzed by electrochemical impedance spectroscopy (EIS) and accelerated corrosion test in a humidity chamber. The results showed similar behaviors between the "nano Zr", colorant and the chromate (Cr III) coating. Therefore this kind of conversion coating is a promising substitute for chromate coatings. Keywords: Nano Zr; Immersion process; Electrodeposited zinc; Hexafluorozirconic alkaline solution. COMPORTAMENTO DA CORROSÃO DE UM REVESTIMENTO DE CONVERSÃO À BASE DE ZIRCÔNIO E CORANTES NO AÇO ZINCADO POR ELETRODEPOSIÇÃO ResumoNo presente estudo, avaliou-se o desempenho de revestimentos à base de zircônio e corante sobre substratos de zinco obtidos por eletrodeposição em meio alcalino, em relação aos revestimentos de cromato (CrIII e CrVI). O revestimento "nano Zr" é obtido através da imersão em solução de conversão à base de ácido hexafluorzircônio. Uma vez que o revestimento "nano Zr" é transparente, a adição de um corante proporciona cor à superfície. Neste caso, o corante, quando aplicado depois do revestimento de conversão, confere cor amarela à superfície. O revestimento produzido melhora a proteção contra a corrosão do substrato. Para este estudo ensaios de espectroscopia de impedância eletroquímica (EIS) e testes em câmara úmida foram feitos. Os resultados mostraram comportamentos semelhantes entre o "Zr nano" e corante e o revestimento cromato (CrIII). Por conseguinte, este tipo de revestimento de conversão é um promissor substituto para os revestimentos de cromatização. Palavras-chave: Nano Zr; Processo de imersão; Zinco eletrodepositado; Solução ácida de hexaflúorzircônio.

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Initiation and growth of modified Zr-based conversion coatings on multi-metal surfaces

Cited by 92 publications

References 37 publications

Review—Conversion Coatings Based on Zirconium and/or Titanium

Review—Conversion Coatings Based on Zirconium and/or Titanium

Role of Intermetallics and Copper in the Deposition of ZrO₂Conversion Coatings on AA6014

Corrosion Behavior of a Conversion Coating Based on Zirconium and Colorants on Galvanized Steel by Electrodeposition

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Initiation and growth of modified Zr-based conversion coatings on multi-metal surfaces

Cited by 92 publications

References 37 publications

Review—Conversion Coatings Based on Zirconium and/or Titanium

Review—Conversion Coatings Based on Zirconium and/or Titanium

Role of Intermetallics and Copper in the Deposition of ZrO2Conversion Coatings on AA6014

Corrosion Behavior of a Conversion Coating Based on Zirconium and Colorants on Galvanized Steel by Electrodeposition

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Role of Intermetallics and Copper in the Deposition of ZrO₂Conversion Coatings on AA6014