Investigating the Corrosive Influence of Chloride Ions on Slag Recovery Machine Inner Guide Wheel in Power Plants

Area of Science:

• Materials Science
• Environmental Engineering
• Corrosion Science

Background:

• Coal-fired power plants utilize wet slag removal systems for zero discharge of desulfurization wastewater (FGD wastewater).
• High chloride (Cl^-) content in FGD wastewater poses significant environmental and material integrity challenges.
• The inner guide wheel material, 20CrMnTi, is susceptible to corrosion in these aggressive environments.

Purpose of the Study:

• To investigate the corrosion behavior of 20CrMnTi material in FGD wastewater with varying chloride concentrations.
• To understand the relationship between chloride concentration and the corrosion rate and mechanism.
• To analyze the composition and structure of corrosion products.

Main Methods:

• Dynamic weight loss measurements to quantify corrosion.
• Electrochemical techniques (e.g., potentiodynamic polarization, electrochemical impedance spectroscopy) to assess corrosion kinetics.
• Surface analysis techniques including X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to characterize corrosion products and surface morphology.

Main Results:

• Corrosion rate of 20CrMnTi increased with chloride concentration up to 20 g/L, exceeding 0.8 mm/a.
• A slight decrease in corrosion rate was observed beyond 20 g/L chloride concentration.
• Corrosion product film density initially increased then decreased with rising chloride levels.
• Identified corrosion products include α-FeOOH, γ-FeOOH, β-FeOOH, Fe₃O₄, and γ-Fe₂O₃.

Conclusions:

• Chloride concentration is a critical factor influencing the corrosion of 20CrMnTi in FGD wastewater.
• The observed corrosion rates indicate a significant material degradation risk for components in contact with this wastewater.
• Understanding the corrosion products is essential for developing effective mitigation strategies.