Electrodeposition intermediate states

Car paints are cured with heat in special oven lines. Electrodeposition coatings (used as anticorrosive primers) contain only small amounts of volatile organic compounds (VOC), whereas intermediate and topcoats release considerable amounts of VOCs. Intermediate coats based on waterborne resins have been developed to decrease VOC emission and are already being used in some automotive plants. Basecoats, as part of base-clear topcoat systems, contain very high amounts of volatile organic solvents. Waterborne basecoats were developed more recently to lower this source of solvent emission. Some car manufacturers are operating pilot lines with the aim of introducing waterborne basecoats into their production processes. Many car producers in the United States and Europe have already switched their topcoat lines over to waterborne basecoats [11.3]. 

Apart from the most electropositive metals, most other metals extracted through molten salt routes are recovered as solids these include many important refractory and other transition metals, the lanthanides, and some actinides. Particularly interesting problems arise in the electrowinning of the refractory metals. Attempts to deposit these metals in a coherent, massive form of theoretical density usually meet with a number of difficulties. Deposits may be dendritic, for example, if electrodeposition proceeds under mass transfer control, or they may be powdery and nonadherent if secondary reactions, such as alkali metal deposition, followed by backreaction with the solute, occurs. Moreover, powdery deposits may also arise if low oxidation states, formed as intermediates during the reduction process, disproportionate in the metal-melt interphase. Charge-transfer-controlled electrodeposition or coupled chemical steps appear to be a prerequisite for obtaining dense, coherent, and adherent deposits. Such deposits have been obtained... 

As Stated earlier the most probable mechanism for Ni and Mo codeposition is the one reported by Podlaha and Landolt [117-120] after X-ray fluorescence analysis of the electrodeposited alloy. Their investigations were performed under controlled mass transport conditions (rotating cylinder electrode). The model assumes that the Ni electrodeposition occurs on the surface not covered by the molybdate ions as a reaction intermediate, by direct reduction of nickel species (all of them being complex of Ni " cations with the citrate anions), independently on the molybdate reaction which can occur only in the presence of nickel species [117-120], The model of the Mo-Ni alloy electrodeposition is described by the following reduction reactions ... 

The reduction of tantalum pentafluoride in the ionic liquid [BMP] [TFSI] involves several intermediates with oxidation states between 5 and 0 [11]. By using the EQCM technique, we could determine the apparent molar masses of the electrodeposited species. 

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