Papers by Keyword: Phosphating

Abstract: This work proposes the development of a niobium phosphate coating (PNb) to replace the zinc phosphating, which is very aggressive to the environment and human health. The metallic material utilized was carbon steel (SAE 1010), which was coated with sunbathing - gel containing phosphate and niobium. A traditional zinc phosphate coating was used for comparison of results. The samples were characterized by scanning electron microscopy (SEM), dispersive energy spectroscopy (DES), open circuit potential, electrochemical impedance spectroscopy and anodic polarization. The results demonstrated that the samples coated with niobium phosphate have more surface nobility and greater corrosion resistance.

Abstract: The electrochemical behavior of pure Mg in H₃PO₄ acid (0.42 M) and phosphating solution (0.42 M H₃PO₄+0.34 M ZnO) was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curve and XRD measurements. The results show that Mg has higher corrosion resistance in the phosphating solution than that in the H₃PO₄ acid which may be due to the relative protective phosphating film on the surface.

Abstract: It had validated by experiments why appending rare earth nitrate (REN) into the bath affects notably on development of coating-forming, corrosion resistance as well as on urgency varieties of appearance and component of the coating. The causation rests with the fact that REN not only makes metal surface depolarized and cathodic reactions accelerated, but also acts as crystal nucleus with gel forms on the metal surface to speed up the coating-forming and develop the anti-corrosion capacity of the coating. The optimal level of addition of REN is 30-55 mg·L^-1.

Abstract: Zinc phosphate coating is commonly used for corrosion protection of metallic materials, mainly mild steel. In this study, influence of the pH of phosphating bath on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different pH values (1.75 ~ 2.75). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coating was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that better surface coverage and corrosion resistance for the steel phosphated at pH 2.75.

Abstract: The influence of phosphating temperature on the surface morphology and corrosion resistance of zinc phosphate coatings on mild steel was investigated. The phosphate layers were deposited on steel from phosphating bath at different temperatures (45 ~ 75 C). The surface morphology and composition of phosphate coatings were investigated via scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX). The corrosion resistance of the coatings was evaluated by polarization curves (anodic and cathodic) in an aerated 3.5% NaCl solution. The results showed that the increase in temperature of the phosphating bath up to 55 C caused an increase in surface coverage and in turn resulted in better corrosion resistance. At high temperature (65 °C and 75 °C) the deposition coverage decreased indicating that the best coverage for the phosphate layer on the metal surface was achieved at 55 °C

Abstract: For the ratio from orthogonal experiment, the phosphating solution which prepared with zinc oxide, phosphate acid, tartaric acid, sodium molybdate, Ma Jif salt, sodium fluoride, phytic acid, chrome alum to do the single factor variable experiments. For the various factors effect on the corrosion resistance of phosphating film to do the in-depth analysis. Preliminary analyse the film formation mechanism via the scan curve of the potential to the time, and determined the best film-forming time.

Abstract: This study through a lot of theoretical analysis and experimental exploration, come to add phytic acid and chromium alum in the traditional zinc phosphating solution for phosphating solution film-forming speed and improve the film density has a distinct effect, and further by orthogonal experiments and the final assessment of preferred a group of environmental, low-temperature, and no sediment of new phosphating process. The composition of the phosphating solution is as follow: zinc oxide 0.5g/L; phosphating acid 5.0mL/L; tartaric acid 0.75g/L; sodium molybdate 0.6g/L; Ma Jif salt 2.0g/L; NaF 0.25g/L; phytic acid 0.4mL/L; chromium alum 1.0g/L; free acidity 2-4 points; total acidity 15-18 points. The experimental results show that: the new phosphating process of this study reduces the handling costs, the stability bath performance, little changes in acidity, in the case of do not need to adjust the surface at room temperature, to forming a completed, dense, strong corrosion-resistant color phosphate crystal film on metal surface within 5 minutes, the copper sulfate bit time is 2.5mins, with good adhesion to 0, the impact resistance is 50kg/cm, it can be used in conjunction with a variety of coating processes.

Abstract: Silane treatment is a new method of coating pretreatment, its mechanism, process, traits and problems in the applications were studied. Compared with the traditional phosphating treatment, silane treatment has the characteristics of non-pollution, simple operation, energy saving and environmental protection, and can substitute for the phosphating treatment and has a great development potential.

Abstract: The silane films are fabricated by dipping cast aluminum alloy in silane solution, then curing films. The corrosion resistance of single silane film, composite silane film is compared with phosphating film through acid dropping test, salt water immersion test and electrochemical impedance test (EIS), the results shows that the silane films are obviously superior to the phosphating films in terms of the corrosion resistance of acid solution and neutral salt solution, particularly the corrosion resistance of composite silane films is much better than sigle silane films; corrosion polarization curves show that the corrosion tendency of KH550+KH567 composite silane film is minimum, corrosion rate is yet minimal, corrosion process of this silane films is controled by diffusion step. The corrosion process of uncoated aluminum substrate, KH550 silane films, phosphating films are controlled by electrochemical step. The impedance of phosphate films are lower than the silane films. Appropriate silane treatment can effectively improve adhesion between the coating and the Al substrate. The adhesion between silane film and paint film is firmer than the phosphate film, so silane film is an excellent replacement to phosphate film for painting pre-treatment.

Abstract: Several rust-transforming reagents based on phosphating technology were studied. The reagents respectively contained potassium ferrocyanide, aromatic oximes (SO) or amide material (GA). By dripping CuSO4 test, linear polarization and polarization curves test, the anti-corrotion performance of phosphate coating were characterized. The results showed that: GA and SO could improve the anti-corrosion performance of phosphate coating. SO restrained the dissolution of metal relying on strong chelation, and the restrained effect of GA depended on durative oxidation and chelation. Comparing to SO, GA could enhance the density of phosphating coating significantly. In addition, the chelation of potassium ferrocyanide had little effect with the anti-corrosion performance.