DEVELOPMENT AND CHARACTERIZATION OF ZINC/NICKEL AND ZINC/NIOBIUM PHOSPHATE LAYERS / Desenvolvimento e caracterização de camadas de fosfato de zinco/níquel e zinco/nióbio

AUTOR(ES)
DATA DE PUBLICAÇÃO

2008

RESUMO

In the present study, the viability of the substitution of nickel found in some phosphating baths by niobates or by ammonium and niobium oxalate (Ox) with benzotriazole (BTAH), was investigated. The possible substitution of chromium hexavalent as passivating agent by Ox, was also evaluated. The results showed that the niobium compounds might replace the nickel from phosphating baths with many advantages, mainly due to the non toxic properties of these compounds. The phosphate layers obtained in the baths with niobium compounds presented better properties comparatively to that obtained in the nickel containing bath used as reference. The phosphate layers mass obtained in the baths with niobium compounds was superior to that deposited in the nickel containing ones, and were obtained at lower phosphating periods. Increased corrosion resistance and better protection efficiency were associated to the phosphate layers obtained in the baths with niobates (PZn+Nb) or niobium and ammonium oxalate with benzotriazole (PZn+Ox+BTAH), comparatively to that produced in the bath with nickel (PZn+Ni). The better protection properties of the phosphate layers obtained in the niobium compounds and benzotriazole containing solutions were related to the morphology of the deposited crystals, the phosphate layer thickness and the porosity of these layers. The results also showed that the Ox tested can be used as a sealing compound for phosphate layers and might replace the passivating CrO3, with the advantage of being ambientally friendly, resulting in increased corrosion resistance of the phosphate layer obtained in the solution with nickel (PZn+Ni).

ASSUNTO(S)

nióbio níquel fosfato de zinco fosfato de zinco passivador fosfatização passivador fosfatização níquel nióbio

ACESSO AO ARTIGO

Documentos Relacionados