| With the development of society and technology, the demand of Eco-balance and the improvement of living standard, more and more requirements on the automobile coating with good quality, low cost and friendly environment have been the highlight. Acrylic auto-primer autodeposition coating (also called autodeposition lacquer) is a kind of latex lacquer, which is a sort of water-borne. Acrylic autodeposition lacquer has many good features, such as high organic solvent resistant, high corrosion resistant, no organic solvent and high stability, the low investment cost, etc. The above mentioned characteristics make it produce more economical and social benefits,and satisfy the demand for environmental protection, so it will obtain rapid development.Up to now, the preparation and coating process of auto-primer autodeposition coating still have the main following problems at home and abroad: 1,The performance of the lacquer film's salt spray resistance and its resist organic solvent are not good enough, and it can not combine with the middle coat effectively; 2,It is difficult to control the activity and stability of latex baths during the process; 3,During the process of coating, a solution containing chromium is used to passivate to achieve a better corrosion resistance. However, it also brings difficulties to circumstance protection and liquid waste disposal. These disadvantages have greatly prevented the development of auto-primer autodeposition coating.In this paper, the research on a new acrylic auto-primer autodeposition coating process was discussed, which was originally required by some domestic auto factory. The research is focused on a new process system by using a new acrylic auto-primer autodeposition coating process, without the traditional Chromium passivation procedure. The target of this auto-primer coating is to have better surface quality and corrosion resistance, in order to meet the requirement of export and environment protection.A customized latex for acrylic autodeposition coating was elaborated, which is produced with the combination of the special cross bonding agent. A very good thermosetting film coating could be achieved from the activation autodeposition acrylic latex was prepared. Latex, the carbon black solution, and activate agent. In addition, the process for producing latex and polymerization was optimized, and the influence of the coating conditions and directions on the quality of film coating was fully studied. Based on this research, some good film coatings were found. Finally, the result of this research has been applied in some production and achieved considerable economic and social benefits.The experiments and the outcomes of the practical production are analyzed, and the results are as follows:1,By adding some quantitative tungstate sodium, the final formed coating has better corrosion resistance ability, which results in omitting the previous contain chromium passivation procedure. Therefore, the problem about environment pollution has been resolved as well.2,A new Special Soft monomer A6 was chosen, and the directions for producing latex monomer were optimized, which greatly improved the conglutination force of coating film to the metal and the flexility of coating film, etc. Hence, the salt spray resistance performance of the coating was consequently improved.3,A suitable cross bonding agent to this system to gain a latex paint with higher cross bond was chosen; with self-regulating latex fitting for this acrylic autodeposition coating system, suitable granule diameter and new-style thermosetting acrylic latex with good solidified capability are produced.4,Due to adding a special steady agent, the content of ferric ions is stable within some range. Therefore, no deposit agents was added to the baths to decrease the content of the ferric ions, and the ferric ions does not need to be eliminated timely. In this way, the problem about the activity and stability of latex baths have been resolved successfully, and costs has been reduced significantly.5,In the mixture monomers, the surface quality of the latex is more exquisite if adding the tetraethylene glycol.6,The autodeposited coating belongs to a new-style thermosetting autodeposition coating, which integrates the middle film coating better and has more corrosion resistance than the thermoplastic. This feature is very important to promote this autodeposited coating to market.7,Research on the conditions of coating process provide the whole plan for the foundation of product line in practical production. And the reliable coating process rules can be formulated by practical modifications.The innovation of the research is to cancel the existing contain chromium passivation working procedure during coating process. Under the optimized process, a better surface quality and corrosion resistance ability of auto-primer coating is achieved. This new-style autodeposition coatings and coating process condition have been applied to several domestic auto product lines, and have contributed to improve the auto quality. |
