Study On Preparation And Coating Process Of The New-style Autodeposition Baths For Auto-primer

Autodeposition coating, which is a new-style aqueous paint coating process, has been widely used over twenty years. Different from electrodeposition paint, autodeposition coating can deposit on a metallic surface only by chemical or physico-chemical process without electric power. So it has wide prospects in the auto-primer coating industry. Up to now, the widely used autodeposition coating by auto-manufacturers at home and abroad is thermoplastic. But its coat has a number of serious disadvantages, for example its film coating can not resist organic solvent or well-knit with the middle coat effectively. Moreover, it is difficult to control the activity and stability of latex baths. So these disadvantages have greatly limited the development of autodeposition coatings. In this paper, preparation and coating conditions of new-style autodeposition paint were studied. Using the suitable synthesized latex and a special cross bonding agent, an acrylic latex was prepared. Carbon black solution, latex and oxidizing agent were mixed to prepare a stable autodeposition solution. The thermosetting film coatings were very good after autodeposited on the steel plates. The effects of the monomers, latex accelerator, polymerization process, stirring intensity and cross bonding agents on the quality of the film coating were investigated. In addition, directions for producing latex and polymerization process were optimized. The influence of the coating conditions on the quality of film coating was studied. Based on it, good film coatings were found. This research has applied in the practical production and was good effects. According to requirements for auto-primer by the environment and technology development, new autodeposition acrylic latex baths which are hydrogen peroxide-free and hydrofluoric acid-free were researched. Due to using a better activating agent and acid, the autodeposition baths not only solves those demerits of last one, but also get better film coating with corrosion inhibition. Thus better environment protection and simple processes are gotten. These experiments and the outcomes of the practical production are analyzed. And the results are as follows: (1) Choose a suitable cross bonding agent to this system to gain a latex paint with high cross bond. With fit self-regulating latex to this coating system, suitable granule diameter and new-style thermosetting acrylic latex with good solidified capability are prepared. (2) Due to adding special additive to change the structure of the autodeposited baths, the content of ferric ions is constant within some range, so no deposit agents are added to the baths to decrease the content of the ferric ions and the ferric ions are not need to be eliminated timely. Succeed in solving the problem about the activity and stability of latex baths and reduce costs more effectively. (3) The new-style thermosetting autodeposition coating which integrate the middle film coating better is more corrosion resistance than the thermoplastic. The advantages are very, important to popularize it to market.(4) Research on the conditions of coating process provide the whole plan for the foundation of product line. And reliable coating process rules can be formulated by practical modifications. (5) Applying the academic research to actual industry and realizing economic benefits. (6) Based on it, in order to adapt to the new environmental requirements and overcome those existing shortcomings brought by hydrofluoric acid and hydrogen peroxide, a new-style autodeposition coatings which is hydrogen peroxide-free and hydrofluoric acid-free has been researched and gained a good result was found to prepare actively for practical applications.