[en] Q235b carbon steel, main material of early alkaline radioactive liquid waste tank, can be contaminated by ⁹⁰Sr and ¹³⁷Cs. In this work, batch contamination experiments were conducted to simulate contamination of steel. The results indicated that Fe₃O₄, main corrosion product, fell off to form sludges. Furthermore, Sr existed mainly in form of SrCO₃ in oxide layer and sludge, and the corrosion made Sr enter into corrosion defects. While Cs was more limited to surface, mainly in form of CsNO₃ on the surface of oxide layer and sludge. The findings of this work will facilitate the development of efficient decontamination techniques. (author)