Corrosion behavior and immobilization of pure aluminum and Al-Mg alloy LLRW in magnesium potassium phosphate cements

Magnesium potassium phosphate cement (MKPC) is a candidate material to replace ordinary Portland cement (OPC) for the encapsulation of metallic low-level radioactive waste (LLRW) and improve the corrosion behavior of encapsulated reactive metals such as aluminum. The objectives of this research were to study the corrosion behavior of pure Al (A1050) and Al-Mg alloy (AA5754) embedded in MKPC and OPC mortars, to assess the effect of curing conditions on hardening properties and on the reactivity of Al and Al-Mg alloy. Results were obtained with measurements of compressive strength, X-ray diffraction and polarization resistance and the proposed interpretation was based on Faraday ' s law. In the first 15 days of interaction in water immersion the corrosion rate and the volume of hydrogen evolved were seen to be at least one order of magnitude lower for AA5754 in MKPC than in OPC mortar, yielding average corrosion current density values of 1.85 and 109.0 x 10-6 A/cm2, and hydrogen volumes of 0.33 L/m2 and 17.8 L/m2 for AA5754/MKPC and AA5754/OPC, respectively. The pore pH was close to neutral and the hardening properties were highly dependent on the curing conditions.

Automated summary

Magnesium potassium phosphate cement (MKPC) is a potential replacement for ordinary Portland cement (OPC) in the encapsulation of low-level radioactive waste and improvement of the corrosion behavior of reactive metals. This study investigated the corrosion behavior of pure aluminum (A1050) and aluminum-magnesium alloy (AA5754) in MKPC and OPC mortars, and assessed the effect of curing conditions on the hardening properties and reactivity of these metals. The results showed that AA5754 exhibited significantly lower corrosion rate and hydrogen evolution in MKPC compared to OPC, with average corrosion current density values of 1.85 and 109.0 x 10-6 A/cm2, and hydrogen volumes of 0.33 L/m2 and 17.8 L/m2 for AA5754/MKPC and AA5754/OPC, respectively. The pH of the pores was close to neutral and the hardening properties were highly influenced by the curing conditions.