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<p class="AMSmaintext2">A significant amount of scale is produced during casting of ingots and processing of hot-rolled products. In manufacturing steel, during the various rolling operations, the amount of scale produced is approximately 0.1% of the annual production of the rolling mills. The quality of the thin sheet during rolling is affected by the behavior of the iron oxide layers formed on their surfaces. For this reason, acids and oils are used for the descaling of slabs and billets by means of pressurized water. The calamine, contaminated by these various acids and used oils, is rejected and stored involuntarily on important areas and pollutes soil and groundwater. Micrographic observations as well as X-ray diffraction analysis have shown that calamine consists mainly of iron oxides. Hematite and magnetite become the main components for oxidation times greater than 1 hour. Characterization tests have shown that calamine is dense (ρ = 4.8 g/cm³), its particle size is variable depending on the degree of oxidation (from 0.5 to 10 mm). Simultaneous thermal analysis showed that an increase in mass of the calamine sample with a release of heat. Studies are underway for the physico-chemical characterization of the soils of the storage areas.</p>

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The objective of this work is to characterize two materials in order to synthesize anticorrosive coating. These materials are an oolitic iron oxide pigment containing phosphorus and scale witch is a by-product of steel making that should be recycled. The characterization of these two components took place in the URASM/CRTI-Annaba laboratories. Chemical analysis showed that the pigment contains 53.18% iron and a siliceous gangue. The scale contains 73.83% iron as iron oxides (FeO, Fe 3 O 4 and Fe 2 O 3).Grinding tests have shown that the scale is much more suitable for grinding than pigment. Particle size analysis gave a volume distribution of particles ranging in size from 0.7 to 32 microns for the scale and from 0.6 to 40 microns for the pigment; their specific surfaces are between 1.6 and 1.5 m 2 /g. TGA and DTA analyzes have shown that the pigment loses weight with phase dissolution by consuming energy as the temperature increases. Scale is gaining weight by forming a new phase with heat. At SEM, the iron pigment is in the form of an aggregate of grains surrounded by gangue. Scale showed a homogeneous structure composed of iron oxide grains of sizes and shapes ranging from 1 to 10 μm. X-ray diffraction analysis showed that the iron contained in the pigment was in the form of hematite and goethite. A tiny portion is combined with silica as Fe 2 SiO 4. Iron in Scale is in the form of three oxides (FeO, Fe 2 O 3 and Fe 3 O 4). Spectrophotometric tests showed that for both materials absorption is nil and reflection is maximal (100%) in the visible range. The different coating formulations used have shown that a mixture of 71.43% pigments and 28.57% scale has the best corrosion resistance, resulting in low current and low corrosion rate.

The corrosion behaviour of X80 steel samples rolled and other quench-tempered in 3.5% NaCl have been studied. Optical microscopy, scanning electron microscopy, potentiodynamic polarization tests and electrochemical impedance measurements are the techniques used to characterize the samples. The results show that the tempered steel has a low corrosion current density compared to the rolled steel. The impedance measurements show the presence of a single capacitive loop attributed to the load transfer phenomenon.