Cadmium Substitution - garteur

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GARTEUR LIMITED <strong>Cadmium</strong> coated bolt and nut 1 st installation 15 th installation PVD aluminium coated bolt and nut 1 st installation 15 th installation PVD aluminium - 5% magnesium coated bolt and nut 1 st installation 15 th installation Figure I3; Torque-tension relationships for steel fasteners coated with cadmium, aluminium or aluminium - 5% magnesium on the 1 st and 15 th installations Page 104 GARTEUR SM/AG17 TP128
GARTEUR LIMITED ANNEX J Coating repair J.1 Introduction The use of brush plating for the repair of electrodeposited zinc-nickel, zinc-cobalt-iron and PVD aluminium coatings was investigated. The approach adopted was as follows: J.2 Experimental • Establish the corrosion resistance of brush plated coatings in comparison with bath applied coatings • Examine the corrosion resistance of coated panels which had been damaged and then repaired by brush plating J.2.1 Brush plating of mild steel panels A series of trials were conducted initially using commercially available cadmium and alkaline zinc-nickel brush plating electrolytes and experimental acid zinc-cobalt and acid zinc-nickel electrolytes. Mild steel 1mm thick 50mm x 50mm panels were brush plated to produce coatings of various thicknesses in the range 5 to 25μm. Tape pull-off tests were performed on several of the coated samples to check coating adhesion. Neutral salt fog trials were also conducted and the time to red rust recorded. J.2.2 Brush plating of damaged panels J.3 Results Coated panels prepared for the Garteur programme were first damaged by removing a portion of the deposited layer in the centre of the test panel. They were then re-plated in the damaged region itself and around the edge of the original coating with either zincnickel, zinc-cobalt alloy or cadmium coatings (see figure J1) according to the matrix in table J1. The adhesion of electrodeposited coatings to aluminium substrates is frequently poor because of the presence of the surface oxide film. Several samples of the panels coated with PVD aluminium were treated prior to re-plating with cotton swabs containing zincate solution. The zincate process employed was a relatively simple, cheap and reliable technique that has often found use when there is a requirement to plate onto aluminium. The corrosion resistance of the re-plated panels was established using neutral salt spray tests. J.3.1 Brush plated mild steel panels Each of the electrolytes evaluated was found to provide suitable coatings in the required thickness ranges. The zinc-nickel and cadmium coatings were found to be semi-bright at best, whereas the zinc-cobalt coatings were bright in appearance. In the tape pull-off tests no signs of adhesion failure were observed. The results of the neutral salt fog tests made on coatings nominally 7-8μm thick are summarised in table J2. The data indicate that the brush plated zinc-cobalt coating provides the highest level of corrosion protection. The two zinc-nickel coatings examined were less effective than GARTEUR SM/AG17 TP128 Page 105
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GARTEUR LIMITED This page is intent
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GARTEUR LIMITED Executive summary B
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GARTEUR LIMITED nickel coatings cou
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GARTEUR LIMITED G.1 Introduction 89
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GARTEUR LIMITED The various aims of
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GARTEUR LIMITED 11 Tables Coating t
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GARTEUR LIMITED Coating Thickness
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GARTEUR LIMITED As plated Passivate
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GARTEUR LIMITED Properties ED Zn-Co
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GARTEUR LIMITED A.2.4 Delta-tone/De
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GARTEUR LIMITED A.4 Tables Coating
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GARTEUR LIMITED 1 Abrasive blast us
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GARTEUR LIMITED 1 Activation bath (
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GARTEUR LIMITED B.3.3 Coating Adhes
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GARTEUR LIMITED Type A Measurements
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Cadmium Substitution - garteur

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