Description
Corrosion prevention of metallic surfaces is an essential factor in the economic utilization of steel. Among the wide variety of surface treatments of metallic surfaces against corrosion, galvanizing (process of immersing steel into a bath of molten zinc to apply a protective coating) provides ideal rust protection for steel. No other coating match galvanizing’s unique combination of low initial cost, durability, low maintenance and resistance to abrasion and mechanical damage, that’s why galvanizing is currently used for several applications: building and construction, street furniture, industrial equipment, etc. Final passivation of galvanized steel with chromium VI is currently applied to provide better corrosion protection, but chromium VI is a metal of very high concern for human health and environment. Although several regulations has restricted or ban its use, it is not totally restricted. Large amounts of chromium VI used for the passivation of galvanized steel are distributed in the planet, becoming a potential source of contamination. The objective of the project is to develop a chromium free passivation treatment for galvanized steel.
Summary of project results
The restrictions on the use of traditional pre-treatments for corrosion protection have been strictly limited due to both human health and environmental concerns. The need of alternatives to conventional protection systems is the origin of this project, which aims the development of a chromium-free passivation system, for galvanized steel, with improved corrosion protection properties and a low environmental impact. A new process based on an inorganic compound has been described as a chromium-free passivation system, used after a water quenching bath to reduce the temperature of the pieces. If necessary, the product can be dissolved in the quenching bath as in many of South America plants which are using chromium products. Following the results of potentimetric test the product applied on hot dip galvanized yields a pasivated surface with an inhibition potential as good as the obtained with chromium products. The new product will be sold in South America next months.
Summary of bilateral results