Obtaining zinc coating and zinc alloys by electro-deposition using modulated current, its passivation via process devoid of CrVI followed by application of water-based resin

• Grant number: 00/13402-0
• Support Opportunities: Research Grants - Innovative Research in Small Business - PIPE
• Start date: August 01, 2002
• End date: March 31, 2003
• Field of knowledge: Engineering - Materials and Metallurgical Engineering - Transformation Metallurgy
• Principal Investigator: Célia Regina Tomachuk dos Santos Catuogno
• Grantee: Célia Regina Tomachuk dos Santos Catuogno
• Company: Tecnozinco Tratamento Superficial Ltda
• City: Indaiatuba

Abstract

Alloys of zinc with metals from the eighth group have been replacing layers of pure zinc in applications which require high resistance to corrosion. As with zinc coatings, zinc alloys are also chromatized with subsequent application of a layer of resin. The project in question proposes to develop layers of ZnNi, ZnCo and ZnFe electrodeposited using baths free from cyanides on a substrate of carbon steel using modulated current deposition techniques. Modulated current allows better control of the composition of the alloy deposits, as well as savings in the quantity of salts and additives used in the preparation of the baths. Subsequently, a post treatment will be carried out with alternative products to chromates, such as molibdates and rare earths and, in replacement for commonly used resins, water-based varnishes will be researched. The search for alternative passivants is with the aim of bringing the products up to international standards in terms of environmental protection. The efficiency of the process with modulated current will be compared with the traditional process through reproducibility, savings on deposition time and chemical compounds, measurements of thickness of layer, the morphology of the deposit and the composition of the deposition solutions. The resistance to corrosion of passivated coatings will be analyzed with electrochemical techniques: polarization curves and spectroscopy - of electrochemical impedance and by in camera exposure to saline fog. It is intended to develop a mathematical model to quantify the protective value of Zn coatings and Zn alloys in a given medium. The performance of the electrodeposits will be compared with coatings passivated with hexavalent chrome and organic resins. (AU)