Study On Key Factors Of Cleaner Production In Pickling Of Hot Rolling Carbon Steel

Cleaner production in pickling is always a pursuing goal of steel industry, and the research of key factors is an hot point. Adding inhibitors is one of the most effective technical methods to answer the requirements of cleaner production in pickling, but it is barely that study on the interrelationship and interaction among oxide layer on the hot rolling carbon steel,corrosion temperature, concentration of corrodent and inhibitors.The oxide layer was prepared by simulating test of hot rolling process in this paper. Its thickness and phase composition were measured by metalloscope and X-ray diffraction(XRD).Inhibition performance, adsorption model and thermodynamic of Polyoxyethylene octylphenol ether(OP-10),Hexamethylene tetramine(HA) and Polyepoxy-succinic acid(PESA) to A3carbon steel in2M HC1were investigated with the weight loss methods.The effect of oxide layer on the hot rolling carbon steel,corrosion temperature, concentration of corrodent on corrosion inhibition and electrochemical behavior for A3carbon steel, as well as adsorption stability were studied by electrochemical method. Corrosion morphologies compared with matrix steel were observed by Scanning Electron Microscope(SEM) and Energy Disperse Spectroscopy(EDS).This paper aims at studying the key factors of cleaner production in pickling in order to provide the data base and theory basis for cleaner production in pickling.The experimental results indicate that the thickness of the oxide layer in the center here is10-12μm and the edge thickness is up to25μ m.The scale is mainly magnetite, containing a small number of hematite, while barely ferrous oxide. The adsorption of PESA, HA and PESA accord with Langmuir adsorption isotherm.The inhibition efficiency of OP-10and PESA belong to the mix type inhibitors decreasing with the increasing temperature, while HA belong to the anode type corrosion inhibitor increasing with the increasing temperature.Corrosion inhibition of PESA, HA and PESA decreasing when the effect of corrosion inhibition reach to a certain extent, manifest that the pickling process consist of three sections:the acid corrosion in the initial stage of corrosion, the effect of inhibitor subsequently and the desorption of inhibitors.The existence of the oxide layer greatly contribute to the cathode process of matrix steel, which is greater than anode, changing the adsorption thermodynamic state of inhibitors, and to make the desorption of inhibitors difficult and the velocity of desorption faster. In the corrosion inhibition system to the carbon steel with oxide layer, temperature increasing is in favor of the absorption of OP-10and PESA, while it goes against HA.The tendency is opposite to the system of matrix steel.In the corrosion inhibition system of carbon steel with oxide layer under the extreme condition(6M hydrochloric acid),it is illustrated that the adsorption of OP-10and HA are unstable and desorbed easily, and the adsorption of PESA is better and more stable when the concentration of PESA increasing. PESA suffice to resis the extreme condition and has a brilliant market developing prospect.The protective film of matrix formed by inhibitor after corrosion is compacted, uniform and stable, while film of carbon steel with oxide layer baring local matrix is loose, and the compactness and rust-proof in the air are bad.