Research on Pickling Passivation Solution and Related Technology for Aluminized Stainless Steel Pipe

With the elements to be adjusted，including nitric acid，hydrofluoric acid，sulfuric acid，hydrochloric acid，the corrosion inhibitor and the additive，the orthogonal test and the visual method are performed to evaluate the pickling passivation quality， optimize the passivation solution ratio， and observe the thickness changes of the aluminized layer of the stainless steel pipe as developed with different pickling passivation operation time. As a result， it is identified that the aluminized layer has a satisfactory pickling passivation quality with the solution containing 10% nitric acid， 5% hydrofluoric acid， 5% hydrochloric acid， 5% sulfuric acid， 0.75% corrosion inhibitor and 0.5% additive. And with such solution to pickle the pipe for just 2 minutes，oxide scale can be removed quickly and effectively without any damage to the aluminized layer， and after operation for 30 minutes， the aluminized layer thickness still remains as over 20 μm，and the layer proper is uniform and dense，while the surface of stainless steel tube looks pretty smooth and bright.