Electroless Ni–P plating on AZ91D magnesium alloy from a sulfate solution

Gu, Chao; Lian, Jianshe; Li, Guangyu; Niu, Liyuan; Jiang, Zhonghao

doi:10.1016/j.jallcom.2004.07.083

Cited by 137 publications

(71 citation statements)

References 14 publications

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“…Various techniques have been developed for applying a protective coating to the surface, such as: electrochemical deposition, chemical deposition, conversion coating, anodizing, organic coating, and deposition processes from the vapor phase [2]. Electrodeposition and chemical deposition enable the easy formation of corrosion-resistant film on the magnesium alloy surface [3,4] by reduction of the metal cations in the solutions of metal ions. However, two main reasons are responsible for difficulties encountered as a result of both kinds of deposition on magnesium alloys [5,6].…”

Section: Introductionmentioning

confidence: 99%

Effective and Environmentally Friendly Nickel Coating on the Magnesium Alloy

Rončević

Buzuk

Vladislavić

2016

Metals

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Abstract:The low density and good mechanical properties make magnesium and its alloys attractive construction materials in the electronics, automotive, and aerospace industry, together with application in medicine due to their biocompatibility. Magnesium AZ91D alloy is an alloy with a high content of aluminum, whose mechanical properties overshadow the low corrosion resistance caused by the composition of the alloy and the existence of two phases: α magnesium matrix and β magnesium aluminum intermetallic compound. To improve the corrosion resistance, it is necessary to find an effective protection method for the alloy surface. Knowing and predicting electrochemical processes is an essential for the design and optimization of protective coatings on magnesium and its alloys. In this work, the formations of nickel protective coatings on the magnesium AZ91D alloy surface by electrodeposition and chemical deposition, are presented. For this purpose, environmentally friendly electrolytes were used. The corrosion resistance of the protected alloy was determined in chloride medium using appropriate electrochemical techniques. Characterization of the surface was performed with highly sophisticated surface-analytical methods.

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Section: Introductionmentioning

confidence: 99%

Effective and Environmentally Friendly Nickel Coating on the Magnesium Alloy

Rončević

Buzuk

Vladislavić

2016

Metals

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“…[26][27] However, this flat and leveled off surface resulting from the protection of the insouble film (MgF 2 ) at high concentrations of F − generates a decrease in mechanical interlocking action between the coating and the substrate, resulting in poor adhesion as listed in column MIIA and MIIB in Table II. 48 The adhesions of the Ni-P coatings obtained at low concentrations of F − are slightly better because of the interlocking action. However, this adhesion obtained at low concentrations of F − is still unsatisfactory since the formed oxide film on the surface of the substrate cannot be removed adequately and the substrate cannot be protected by trace quantities of magnesium fluoride.…”

Section: Journal Of Thementioning

confidence: 98%

“…This microstructure on the substrate surface provides not only more chemical active sites for the ENP, but also surface pits for mechanically interlocking and improving coating adhesion. 17,48 These ideas are consolidated by the data listed in the columns of MIIIA and MIIIB in Table II. The results of scribe and grid test demonstrate that the Ni-P coatings prepared by an etching process in H 3 PO 4 solution followed by HF or NH 4 HF 2 activation will give wonderful adhesion of ENP on Mg alloy.…”

Section: Journal Of Thementioning

confidence: 99%

Studies of Several Pickling and Activation Processes for Electroless Ni-P Plating on AZ31 Magnesium Alloy

Xie

Chen

Xiang

et al. 2014

J. Electrochem. Soc.

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Several chromium-free pickling and activation processes were investigated in order to develop an eco-friendly pretreatment for electroless Ni-P plating on magnesium alloy. The coatings obtained from etching only in H 3 PO 4 solution exhibit poor adhesion due to the existance of an interlayer. Meanwhile, a corrosion model of Mg alloy in H 3 PO 4 solution was proposed. When fluoride was added into the pickling solution, the adhesion of the coatings was also unsatisfied because of the bad mechanical interlocking action. By comparison, the coatings obtained from pickling in H 3 PO 4 solution followed by NH 4 Magnesium (Mg) alloy is one of the lightest structural metals and a potential candidate to replace the heavier aluminum or steel in manufacturing of mechanic components due to its low density, excellent physical and mechanical properties. [1][2][3][4][5][6] However, the use of Mg alloy for structural applications has been limited owing to their poor corrosion resistance and high chemical reactivity. 7-12Electroless Ni-P plating (ENP) is one of the most effective surface treatment techniques to overcome the defect of Mg alloy, because ENP can provide excellent properties of hardness, good wear resistance and great corrosion resistance by forming a uniform deposit on the Mg alloy substrate surface. [13][14][15][16] However, ENP on Mg alloy presents many problems still because of the rapid formation of oxide film upon Mg alloy exposed to air/water, and forming loose immersion layers on the substrate surface by replacement reactions at the initial deposition stage. The loose oxide film and immersion layers hinder successful ENP and are detrimental to the adhesion and uniformity of subsequent coatings.17-20 Therefore, appropriate pretreatment steps must be taken before ENP to remove the natural oxide tarnish, embedded sand, heavy metal impurities and burned-in lubricants on the surface of the Mg alloy, and to activate the deposition of nickel on the matrix. [21][22][23] There are mainly two types of preferred pretreatments for Mg alloy, including zinc immersion and direct ENP.18,24 The direct ENP is simpler and more convenient.11 However, acid pickling in a chromiumcontaining (VI) solution, followed by activation in a hydrofluoric acid solution is usually employed in the conventional pretreatment processes of direct ENP. [25][26][27][28][29][30] Several modified pretreatments have been devised to avoid the use of such process, which contains some species detrimental to the environment and harmful to human health. 11,[31][32][33] A method of avoiding the use of toxicant was carried out by employing a pre-plating step with an alkaline ENP bath prior to subsequent common ENP in an acidic bath.31 Molybdate (MoO 4 2− ) chemical conversion coating was also attempted for replacing the chromium acid pickling. [32][33] In the work of Ref. 32, strong volatile hydrogen fluoride acid was applied in the activation process and the molybdate conversion bath contained carcinogenic NaNO 2 . 32 The adhesion, which is a very important...

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“…Gu (Gu et al, 2005 and proposed a combination of a nickel electroless intermediate layer plus an electrodeposited layer of nanocrystalline nickel to obtain high corrosion resistance with good wear resistance on magnesium AZ91D (Fig.23).…”

Section: Dual Coatingsmentioning

confidence: 99%