Acidic spent pickling solutions and rinse water are produced during steel pickling. They are usually neutralised with lime in a neutralisation plant and pumped in the form of a wet sludge to a landfill. This is one of the main environmental issues of Russian factories. The implementation of sludge treatment units, including equipment for sludge polymer conditioning and dewatering, is the most relevant task for the purpose impact reduction of factories on human health and environment. The researches results of polymer conditioning of the aggressive wastewater sludges by flocculants are reflected in the paper. Sludge samples were obtained from a neutralisation plant of a machine factory of aerospace industry. Sludges of two types were investigated: the sludge which is formed in clarifiers during spent pickling solutions neutralization with lime; the sludge which is formed in clarifiers during rinse water neutralization with lime. During the work non-ionic, cationic, and anion flocculants Praestol efficiency was estimated. The shortest time of water capillary suction from the flocculated sludge was accepted as efficiency criterion of flocculant processing. It was defined with use of the capillary suction timer Fann and Whatman 17 chromatographic paper. It is established that: non-ionic focculant Praestol 2500 dose of 4–5 g/kg dry solids is effective for conditioning of the sludge produced during lime neutralization of acid spent pickling solutions; the anionic flocculant Praestol 2540 dose of 1.5–2 g/kg dry solids is effective for conditioning of the sludge produced during lime neutralization of acid rinse water. The empirical response surfaces and the contour plots showing the relationship between capillary suction time and a dosage of flocculant and a charge density (% hydrolysis) of a flocculant were reveived. © 2023 American Institute of Physics Inc.. All rights reserved.