The Corrosion of White Cast Iron in Polluted Phosphoric Acid Medium Contains Fluoride Ions

The global demand for phosphoric fertilizers will increase in the coming years, which should boost phosphoric acid production. And to ensure this production, the choice of the right materials and the search for solutions for the costs of corrosion becomes the challenge of the specialists. This is why this research focused on the corrosion resistance of white cast iron in the similar medium of the phosphoric acid production plants containing fluoride ions at 80 °C. And the techniques used are the electrochemical measurements and UV-Vis-NIR spectroscopy, Scanning electron microscopy and energy dispersive spectroscopy analysis, X-ray diffraction analysis (XRD). The results showed that fluorine influences the electrochemical parameters of the system and favors the dissolution of the alloy, in particular at the ferrite matrix. The increases current density value in the passive region and reduces the passive domain, while causing the partial chemical degradation of the passive film at the potential close to 0.5 V/SCE. And that was explained by that fluoride increases the inter-phase corrosion between the ferrite and carbide phases, and increases the dissolution of iron more than Chromium in the solution, which weakens the resistance to corrosion of the alloy.