Abstract: Taking a 20 000 m3 floating roof tank located in the initial station of Weijing Line as an example, a subject of chemical derusting has been studied for on-line oil tank recoating. Through field implement of the chemical derusting technique, it comes to the conclusion that the technique has got the following advantages: safety, simple operation, high derusting rate, low costs, loose working procedure, and especially, suitability for on-line tank recoating in inflammable, explosive environment, and the purposes of safety, availability, cost effectiveness and good quality have been attained.