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Table of contents
GENERAL INTRODUCTION
I. LITERATURE REVIEW
I. 2. Oxidation and pickling in steelmaking process
I. 2. 1. Overview of steelmaking process
I. 2. 2. The hot strip mill
I. 2. 3. The pickling baths
I. 3. Oxidation of steel
I. 3. 1. Steel substrate properties
I. 3. 1. 1. Low carbon steel
I. 3. 1. 2. Silicon alloyed steel
I. 3. 2. Oxidation conditions
I. 3. 2. 1. Oxidation in the Hot Strip Mill
I. 3. 2. 2. Oxidation in a pilot furnace
I. 3. 3. Oxidation of low carbon steel
I. 3. 3. 1. Oxidation kinetics
I. 3. 3. 2. LCS oxidation mechanism
I. 3. 4. Oxidation of silicon alloyed steels
I. 3. 4. 1. Influence of silicon on the kinetics of scale growth
I. 3. 4. 2. Influence of silicon on oxidation mechanism
I. 4. Scale and metal oxides properties
I. 4. 1. Hot strip mill (HSM) scales
I. 4. 1. 1. Low carbon steel (LCS) scales
I. 4. 1. 2. Silicon alloyed steel (SiAS) scales
I. 4. 2. Model scales
I. 4. 2. 1. LCS model scales
I. 4. 2. 2. Iron oxides properties
I. 4. 2. 3. SiAS model scales
I. 5. Pickling and over-pickling
I. 5. 1. Pickling of hot mild steels
I. 5. 1. 1. Pickling conditions
I. 5. 1. 2. Influence of pickling parameters on pickling time
I. 5. 2. Pickling mechanism of low carbon steels
I. 5. 2. 1. Pickling steps of LCS
I. 5. 2. 2. Pickling reactions of LCS
I. 5. 2. 3. Iron oxides dissolution
I. 5. 3. Effect of Silicon on pickling mechanism
I. 5. Conclusions
II. 1. Elaboration of steel grades samples
II. 1. 1 Steel chemical composition
II. 2. 2. Steel grains size
II. 2. Oxidation of steels
II. 2. 1. Oxidation experiments
II. 2. 2. Oxidation methods
II. 3. Scale Characterization after oxidation
II. 3. 1. Optical observations
II. 3. 2. Spectrometric methods
II. 4. Scale dissolution characterization
II. 4. 1. Electrochemical measurements
II. 4. 1. 1. Electrochemical set-up
II. 4. 1. 2. Electrochemical methods
II. 4. 2. ICP-AES setup and method
II. 5. Scale characterization after pickling and over-pickling
III. OXIDATION AND SCALE CHARACTERIZATION OF SILICON ALLOYED STEELS
III. 1. Introduction
III. 2. Steel substrate properties
III. 3. Oxidation mechanisms
III. 3. 1. Low carbon steel oxidation
III. 3. 1. 1. Oxidation kinetics
III. 3. 1. 2. Oxidation mechanism
III. 3. 2. Effect of Silicon content on oxidation
III. 3. 2. 1. Oxidation kinetics
III. 3. 2. 2. Oxidation mechanism
III. 4. Scale characterization
III. 4. 1. Low carbon steel scale properties
III. 4. 2. Silicon steel scales properties
III. 5. Conclusions
IV. PICKLING AND OVER-PICKLING MECHANISMS OF LOW CARBON STEEL.
IV. 1. Introduction
IV. 2. Model scale characteristics before pickling
IV. 3. Electrochemical dissolution of scale
IV. 3. 1. Corrosion potential Ecorr
IV. 3. 2. Corrosion current Icorr
IV. 3. 2. 1. Tafel curves
IV. 3. 2. 2. Corrosion current evolution during scale dissolution
IV. 3. 3. Electrochemical Impedance Spectroscopy EIS
IV. 3. 3. 1. EIS diagrams
IV. 3. 3. 2. Evolution of charge transfer resistance R
IV. 3. 3. 3. Evolution of CPE parameters
IV. 3. 3. 4. Evolution of effective capacitance
IV. 4. Total dissolution of scale
IV. 5. Pickling and over-pickling mechanisms
IV. 5. 1. Pickling thermodynamics
IV. 5. 2. Pickling steps and reactions
IV. 5. 3. Over-pickling reactions
IV. 6. Influence of some parameters on picking and O-P mechanism of LCS scales
IV. 6. 1. Scale composition and morphology
IV. 6. 1. 1. Influence of hematite on pickling
IV. 6. 1. 2. Pickling of an industrial scale
IV. 6. 2. Influence of acid concentration
IV. 6. 3. Influence of pickling bath temperature
IV. 6. 4. Influence of a cathodic applied potential
IV. 7. Steel surface after pickling and over-pickling
IV. 7. 1.Steel surface after insufficient pickling
IV. 7. 2 Steel surface after long over-pickling:
IV. 8. Conclusions
V. PICKLING AND OVER-PICKLING MECHANISMS OF HIGH SILICON ALLOYED STEEL GRADES
V. 1. Introduction
V. 2. Model scale characteristics before pickling
V. 3. Electrochemistry of scale dissolution
V. 3. 1. Corrosion potential Ecorr
V. 3. 2. Corrosion current density Icorr
V. 3. 2. 1. Current-potential curves
V. 3. 2. 1. Evolution of the corrosion current density
V. 4. Total dissolution of scale
V. 4. 1. Total dissolution rate (TDR)
V. 4. 2. Electrochemical contribution in scale dissolution
V. 5. Pickling and over-pickling (O-P) mechanism
V. 5. 1. Pickling steps and reactions
V. 5. 2. Over-pickling steps and reactions
V. 6. Influence of some parameters on picking and O-P mechanism
V. 6. 1. Scale morphology and composition
V. 6. 1. 1. Influence of fayalite morphology
V. 6. 1. 2. Behaviour of industrial scale
V. 6. 2. Influence of pickling bath temperature
V. 6. 3. Influence of acid concentration
V. 7. Steel surface after pickling and over-pickling
V. 7. 1. Steel surface after insufficient pickling
V. 7. 2. Steel surface after over-pickling
V. 8. Conclusions
GENERAL CONCLUSION
ANNEXES
REFERENCES
