Establishment Of The Quality Index Of Sodium Phytate And Preliminary Study On Its Application In Micro-arc Oxidation On Magnesium Alloy

Phytic acid and its sodium salt has strong metal chelating ability, and it is a rare multi-complexing agent for metal ions,and is widely used in daily chemical, food, Surfaces of Metals and etc.But there is no product quality standard of sodium phytate.In order to ensure the application of the sodium phytate in many fields, including metal protection, promote the extension of the fine product,In this paper, we study on the establishment of the quality index for sodium phytate and the effect of its concentration in micro-arc oxidation on magnesium alloy and corrosion resistance.Firstly,referring to the standard of phytic acid, the main series of detection indexs and their range are preliminary determined, such as differential experiment the determination of the content, inorganic phosphorus, chloride, sulfate, calcium salt, lead and arsenic.Through Selection and optimization the test conditions in the determination of the content of sodium phytate,such as the degree of strong acid digestion of sodium phytate,the dosage of nitric acid in Precipitation stage,and the effectiveness of the QMCA; Improvement of inorganic phosphorus detection method,adding ferric chloride precipitation steps, to improve the specificity of detection method; confirmation of the applicability of other detection methods, finally established the conventional physical and chemical method to meet the demand.Secondly, by using the detection methods, the commercially available samples are tested to verify the rationality of initial quality index.The selected samples which the result of inorganic phosphorus and arsenic are exception are verified by the advanced methods such as chromatography and mass spectrometry and so on.It is indicated that the inorganic phosphorus and other quality indicators established have great significance for the identification of the authenticity of sodium phytate.Finally,in this paper, the effect of sodium phytate’s concentration on the microstructure and corrosion resistance of micro arc oxidation coatings on magnesium alloy was studied,we found that:First,with the increase of the concentration of sodium phytate, the electrical conductivity of electrolyte solution and the oxidation end voltage is increased, the thickness of the formed oxide film is more thicker, the porosity of the oxide film formed on the surface of the sample is reduced,and the pore size is increased,and it is more favorable for the formation of the film.The corrosion area of the samples after immersion corrosion in simulated body fluid is the smallest,and the corrosion resistance of the film is the best when the concentration of sodium phytate was 12 g/L.Second, the composition of the micro arc oxidation film formed by the treatment of sodium phytate contains C and P elements, and it is showed that sodium phytate not only plays a role in promoting the formation of the membrane, but also participates in the membrane reaction.The structure of oxide film phase is mainly composed of amorphous phosphides and MgO.With the increase of the concentration of sodium phytate,there is no obvious change in the structure of the oxide film on the surface of the sample.