<p>The long-term performance of concrete structures is inevitably compromised by prolonged exposure to corrosive environmental media. Chemical corrosion reactions and ionic diffusion mechanisms constitute pivotal contributors to concrete deterioration, introducing substantial stochastic variability through internal fluctuations and environmental interactions. In the study, the chemical Langevin reaction–diffusion equation (CLRDE) is derived from the mass conservation law and the random process theory to probabilistically model the evolution of corrosion product contents in concrete subjected to attack by environmental factors. The spatio-temporal evolution of corrosion product contents can be predicted by solving the proposed equation and the corresponding probability information is thoroughly analyzed. To validate the accuracy and effectiveness of this model, three sets of experimental data from sulfate-attacked concrete systems were selected from the literature. The results reveal that the evolution of corrosion product contents exhibits random characteristics across both temporal and spatial scales. The CLRDE provides a comprehensive probabilistic framework for describing this stochastic process, yielding a probabilistic solution for corrosion product contents in concrete at each time and spatial step. Comparative analysis between experimental data and theoretical computations confirms the feasibility and practicability of the proposed method.</p>