To evaluate the effect of chemical cleaning treatment on superheater oxide scale

three typical materials of a supercritical unit superheater

T23

T91 and TP347H

were analyzed before and after chemical cleaning.The corrosion situation

element content and microstructure of the oxide scales were tested by thermogravimetric analysis

energy spectrum analysis and metallographic analysis.The results show that

chemical cleaning can effectively remove the oxide scales on the surface of pipe sheets with removing efficiency over 90%.The oxide scales of T23 steel are mostly iron oxides

which can be totally washed and the metal base can be seen after chemical cleaning.The oxide scales of T91 steel consist of two layers

after chemical cleaning

there are some residues of the inner oxide layer

which is Cr-rich layer.The oxide scales of TP347 Hsteel pipes become thinner considerably after chemical cleaning

and the residue is Cr-rich layer.The T91 steel's anticorrosion performance is the worst

of which the total corrosion amount is18.97g/m2 and the corrosion rate is 0.38g/(m2·h).Then is the T23 steel.The TP347 Hsteel performs the best.Chemical cleaning does not generate intergranular corrosion to austenic steel TP347 H.