influência da adição de diferentes concentrações de bismuto, níquel, estanho e alumínio sobre a espessura de camada, resistência à corrosão e brilho nos revestimentos galvanizados

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Blackeart malleable iron samples were galvanized using twenty different zinc bath compositions. Each bath was made with different concentration and combinations of bismuth, nickel, tin and aluminium. These additions aim not only to substitute lead, a hazardous element to the environment, but also to reduce coating thickness, usually higher than established by standards due to the great reactivity between cast iron and zinc bath. Additional studies were made to check the corrosion resistance and to check the maintenance or intensity of the coatings brightness. When using just bismuth and nickel additions to the zinc bath, it wasnt observed a considerable coating thickness reduction, but bismuth influenced bath fluidity, favoring better zinc draining and formation of more compacted and defined zinc-iron compounds. It was observed that bismuth decreased the coatings corrosion resistance, while nickel can increase the corrosion resistance when the bath has small bismuth concentrations. Tin addictions reduced the coating thickness when used together with bismuth and nickel addictions. However, tin did not only reduce the corrosion resistance, but also decreased the coatings brightness. Highest aluminium concentrations reduced the coatings thickness considerably when compared to the coatings thickness of the samples galvanized in the other baths. Aluminium also increased corrosion resistance when compared to the coatings of the samples galvanized in baths containing bismuth, nickel and tin. However excessive coating thickness reduction, caused by highest aluminium addictions to the bath, reduced corrosion resistance. Highest aluminium addictions were totally favorable to the coatings brightness. The combination of bismuth, nickel, tin and aluminium were effective on coating thickness reduction and some of these combinations also provided greater rust resistance and shinier coatings. Hence, the chemical elements added werent detrimental to the environment and they are good alternatives to substitute lead in the hot-dip galvanizing process.

ASSUNTO(S)

coating thickness engenharia de materiais e metalurgica zinco-ferro e compostos intermetálicos espessura de camada resistência à corrosão galvanização por imersão a quente metais corrosion resistance hot-dip galvanizing zinc-iron intermetallic compounds

ACESSO AO ARTIGO

Documentos Relacionados