A sealing process includes applying a first reactant to a substrate having a porous structure, the first reactant comprising a chromium (III) precursor and a transition metal precursor and applying a second reactant to the first reactant, the second reactant comprising a rare earth element precursor and an alkaline earth element precursor to form reservoirs of trivalent chromium in pore space of the porous structure, and a physical barrier over the substrate and the reservoirs.