Revisão da utilização de aditivos na eletrodeposição de Níquel: efeitos e aplicações

Abstract

Nickel electrodeposites are widely for industrial applications due to their characteristics such as: corrosion, wear and temperature resistence. It is mainly used for decorative coating, functional coating and electroforming. The coating performed depends on deposition parameters. These depositions parameters include the deposition bath, which is mostly composed of chloride, sulfate, sulfamate or Watts baths. The characteristics of the acquired nickel deposit is enhanced by the addition of additives in the deposition baths. The function od aditives varies and can be generally classified as brighteners, refiners, levelers, surface-active agents and hardeners, depending on their role in the deposition process and resulting deposit. In this context, the present work presents an approach to the use of additives in nickel electrodeposition, with regard to the main applications of each type of additive in the production of different classes of nickel coatings, as well as the effects they provide both in the process electroplating as the appearance and/or characteristics of the nickel deposit. A thorough bibliographic review of articles about the influence of additives on nickel electrodeposition is conducted and presented, as well as discussions about the electrodeposition process and deposition baths. The analysies point to saccharin as the most used additive in nickel electrodeposition, acting mainly as a refiner and brightener, and sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) as the main means of obtaining corrosion-resistant nickel. Lastly, extra caution is considered when using additives with sulfur in its composition to avoid codeposition above the tolerated to obtain a nickel coating with desirable characteristics.