Non-Chromate Conversion Coatings for Magnesium Die Castings

Skar, Jan Ivar; Walter, Manfred J.; Albright, Darryl

doi:10.4271/970324

Cited by 7 publications

(5 citation statements)

References 2 publications

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“…The use of phosphate solutions to form a metal phosphate film was an immediate solution but requires acidic conditions for successful implementation. 4 Zirconia and titanium based coatings, which form complex fluoro compounds, are being widely used today and have shown a satisfactory performance compared to chromium based pre-treatments under accelerated conditions, 5 but the use of fluoro based compounds is an area of concern. 6 Of late, water based coatings have begun to gain prominence.…”

Section: Introductionmentioning

confidence: 99%

Graphene based anticorrosive coatings for Cr(vi) replacement

et al. 2015

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Corrosion has been a perennial issue of concern for the steel industry. Chromate conversion coatings are well known pre-treatment coatings for steel but due to environmental concerns and legislations, their use has been restricted. The industrial community, pegged by these legislations, has been long demanding an economically viable and eco-friendly pre-treatment coating alternative, without having to compromise on the durability and corrosion performance of the overall coating system. The present study focuses on evaluation of graphene as an anticorrosive alternative to Cr(VI) based coatings. Graphene, produced by a high shear liquid exfoliation route, upon functionalisation, provides a conductive and nearly impermeable barrier coating. On electrochemical and coating performance evaluation of this coating system, a dramatic improvement in corrosion resistance is observed. The study confirms the environment friendly corrosion protection of steel using functionalised graphene coating.

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Section: Introductionmentioning

confidence: 99%

Graphene based anticorrosive coatings for Cr(vi) replacement

et al. 2015

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“…Magnesium alloys exhibit many attractive properties for automotive and electronics industries. [1][2][3] However, magnesium alloys are highly susceptible to corrosion and wear, which has limited their useful applications. Unfortunately, the natural oxide layer on magnesium surfaces is very loose and cannot offer any effective resistance to corrosion.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, relevant studies have been developed quickly in recent years. 2,3 Before painting, in order to improve the adhesion of the organic topcoat and the prevention of under film corrosion, one of the most effective methods is to form a conversion coating on the surface between the metal and its environment. 2,3,[6][7][8] Among the conversion coatings, phosphating has become popular because of its low toxicity, low cost and simple technics.…”

Section: Introductionmentioning

confidence: 99%

“…2,3 Before painting, in order to improve the adhesion of the organic topcoat and the prevention of under film corrosion, one of the most effective methods is to form a conversion coating on the surface between the metal and its environment. 2,3,[6][7][8] Among the conversion coatings, phosphating has become popular because of its low toxicity, low cost and simple technics. [9][10][11][12][13][14][15][16][17][18] The processes of the phosphating of zinc, electrogalvanised steel, steel and aluminium have been well known, [19][20][21][22][23] whereas phosphating treatment of magnesium and its alloys remains very rarely explored.…”

Section: Introductionmentioning

confidence: 99%

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Preparation and characterisation of composite double phosphate conversion coatings on AZ91D magnesium alloy

et al. 2010

Surface Engineering

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A composite double zinc phosphate conversion coating was obtained via forming a hopeite crystal layer on an amorphous phosphate layer on the AZ91D magnesium alloy. The surface morphology, structure and phase composition of the composite coating were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). As a comparison, the single zinc phosphate coating and the bare substrate were also discussed. The phosphate crystal clusters can form on the amorphous layer densely and fine. According to the open circuit potential (OCP) and potentiodynamic polarisation curve tests, the composite phosphate conversion coating on the AZ91D magnesium alloy yielded the best protective effect compared with the single amorphous layer and crystal layer.

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“…It could protect the base material by providing a barrier layer blocking the corrosive matter arriving the base metal. There were a number of coating techniques for magnesium and its alloys, such as electro-plating, electroless-plating, chemical conversion, laser cladding, anodizing and vapor deposition etc [8][9][10][11][12][13][14]. But these techniques would bring some negative impacts more or less.…”

Section: Introductionmentioning

confidence: 99%

Research on Water Based Coating for Magnesium Alloy

Huang

Zheng

2006

AMR

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Magnesium and its alloys have many applications for theirs excellent physical and mechanical properties. Due to magnesium’s active chemical properties and difficulties in direct painting, a novel environmental protective water based coating was developed, which mainly contains metal flake, silicate, silane and sodium polyphosphate etc. The properties and structure of the coating were investigated by adhesion test, hardness test, heat resistance test, neutral salt spray test and Scanning Electron Microscopy (SEM) et al. Meanwhile, the effect of sodium polyphosphate was also examined by hydrogen evolution test and electrochemical test. Furthermore, the film forming mechanism of the coating was explored by Fourier Transform Infrared spectroscopy (FTIR). Results showed that the coating had a stepped structure which could achieve extraordinary adhesion, 350°C temperature heat resistance, HV0.50/30 210 hardness and 300 hours anti-corrosion time in salt spray test. In the coating, the addition of sodium polyphosphate could greatly improve the corrosion resistance of the coating because of the barrier film formed by sodium polyphosphate. The mechanism of interpenetrating polymer network (IPN) was preliminary put forward based on the results of FTIR.

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Non-Chromate Conversion Coatings for Magnesium Die Castings

Cited by 7 publications

References 2 publications

Graphene based anticorrosive coatings for Cr(vi) replacement

Graphene based anticorrosive coatings for Cr(vi) replacement

Preparation and characterisation of composite double phosphate conversion coatings on AZ91D magnesium alloy

Research on Water Based Coating for Magnesium Alloy

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