The BR-III-2B iron-based coating agent is a composite phosphorizing agent, which enables surface conditioning, phosphorizing and deactivation to be completed in one and same tank. The phosphate coating is solid and even with good resistance to rust. The product is suitable for pre-painting phosphorzing of steel work pieces for automobile, motorcycle, home electric appliance and instrument & meters, and may be applied together with the electrophoresis and painting process.