Deposition of Bronze Coatings

It is shown that the cathodic electrolysis products of melts based on sodium tungstate, in which molybde-num(VI) or tungsten(VI) oxides, lithium or sodium molybdate, tungstate, and carbonate are dissolved, are molybdenum, tungsten, their bronzes and carbides, and carbon. It is found that the phase composition of electrolysis products is determined by the concentration of carbonate in the melt. The conditions are determined for the deposition of galvanic coatings of molybdenum and tungsten carbides on different materials. 

In electronic applications, where it is common to deposit copper and/or copper alloy and tin in sequence, with a nickel diffusion barrier layer, 0.5 fim thick, between the layers present, no failure occurs. Without the nickel layers between bronze/-copper/tin layers themselves, for instance, intermetaUic brittle layer(s) and Kirkendall voids are formed, leading eventually to separation of the coated system and substrate. 

Figure 15.4 Mapping electrochemical material loss against mechanical erosion rates for a nonpassivating surface carbon steel (AISI1020) along with two potentially passivating surfaces of nickel aluminum bronze (NAB) one that has been thermally sprayed by high-velocity oxy-fuel deposition as a coating on carbon steel ( j and another which has been cast (A.). These results were obtained from jet impingement erosion-corrosion tests. Reprinted from Ref. [7]. Copyright (2007) with permission from Elsevier.

The pcirt to be tested is cleaned by wiping with magnesium oxide, rinsed, and wiped dry. It then is clamped in such a way that the surface is at an angle of 45° to the horizontal and 1/4 in. (6.35 mm) below the nozzle. When the tap is opened, a stopwatch is started simultaneously and the solution is permitted to flow until the coating is penetrated. The solution for testing copper or bronze deposits and multiple coatings of copper with nickel contains ... 

Materials systems are used quite widely on automobiles for corrosion protection. For example, clad metals are commonly used in applications such as exterior trim and bumpers (stainless steel clad aluminum), windshield wiper socket (copper/steel/bronze), transition materials to join aluminum to steel (aluminum clad steel), and hydraulic brake line tubing (steel/SS/steel) [37]. A wide range of metallic coatings are produced by spraying, chemical vapor deposition, physical vapor deposition, electrodeposition, and electroless deposition [23-25]. 

The immersion deposit is necessarily somewhat defective, for the reasons already mentioned, though immersion deposits from complex ions are finer grained and more satisfactory than those reduced from aquocations. The zinc coating is, under the best conditions, an acceptable basis for a copper undercoat from the cuprocyanide bath, on which other coatings can be plated, but there is usually a fair proportion of rejects in commercial operation. Other processes similar in principle use tin or bronze immersion coatings. 

The fact that the composition of the speculum deposit must be closely controlled to obtain the best results has been a serious drawback to development. The coating finds uses on decorative hollow-ware, oil lamps and tableware. The bronze deposits with 10 or 20% tin are used lacquered in decorative metal-ware for domestic and personal ornament and, in thick layers to protect hydraulic pit props against corrosion and abrasion. They have also been used with success as undercoatings for nickel-chromium or tin-nickel alloy deposits. 

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