Phosphate as an important chemical products, mainly for the manufacture of high phosphate and compound fertilizer and industrial phosphate. Can be encountered in the production and use of phosphate process phosphoric acid corrosion. In general, free of impurities in pure phosphoric acid, commonly used stainless steel is basically to solve the corrosion problem. ,18-8 Cr-Ni austenitic steels such as optional for storage concentrations of up to 85% cold phosphate concentrations below 5% phosphoric acid can be used in the process equipment; containing Mo 2% -3% of the stainless steel better corrosion resistance, and Mo increased with the steel, phosphoric acid-resistant performance.
However, phosphate encountered in the wet-process phosphoric acid production process, many contain various impurities, such as the F-, Cl-, SO42-, of Fe3 + and Al3 + and Mg2 + and other. Which, in addition to Fe3 + World pipe network reported that the world's steel pipe network to provide the world's steel pipe network editor , both to accelerate the corrosion of the stainless steel, especially the F-, Cl - is more intense. In order to improve the corrosion resistance of stainless steel in phosphoric acid containing various impurities and improve the steel of Cr and Mo content in the most effective and the Cr was more effective. Domestic test of Cr of the most significant impact; role of Mo, only when the steel containing Cr content is low (for example, 20% ~ 21%) when effective; the role of steel Ni Cr, Mo, high not significant. In H3PO4 containing F-, Cl-and other impurities, in addition to a large number of selection with Mo duplex stainless steel containing Mo 2% to 4% 0Cr17Ni12Mo2, 00Cr17Ni14Mo2 0Cr19Ni13Mo3 World Steel Pipe News , 00Cr19Ni13Mo3 outside, with Cr content ≥ 22%, such as 0Cr26Ni6Mo2Cu3, 00Cr22Ni6Mo2N structure of grade 00Cr25Ni7Mo3N, Mo, Cr-Ni austenitic stainless steel 00Cr20Ni25Mo4.5Cu (N) were also widely available. Without Ni or with only a small amount of Ni in high-chromium ferritic stainless steels, such as 00Cr26Mo1, 00Cr30Mo2 00Cr29Ni2Mo4, 00Cr29Ni4Mo2, etc., due to their resistance to the excellent performance of phosphoric acid containing impurities, but also has broad prospects for the corrosion resistant material. α + γ duplex stainless steel is not only the nature of good corrosion resistance and high strength, which is often used as applied to abrasion erosion material containing impurities H3PO4 has been duly noted. Research and practical application of the results showed that with Cr content up to ~ 27% and high co-austenitic stainless steel containing Mo 00Cr27Ni31Mo3Cu and 00Cr26Ni35Mo3Cu resistance including the best F-, Cl-impurities such as H3PO4 corrosion of the best and comprehensive performance high-grade stainless steel, can be used in the manufacture of H3PO4 concentrated heat exchanger to replace the fragile graphite heat exchangers.