TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The solution in the treating step, comprises at least one strong protic acid. The strong protic acid is based on phosphoric acid and/or sulfuric acid. The phosphoric acid comprises polyphosphoric acid, phosphonic acid, orthophosphoric acid, pyrophosphoric acid, triphosphoric acid, metaphosphoric acid or their derivatives.    TECHNOLOGY FOCUS - POLYMERS - Preferred Process: The process comprises either producing a film comprising at least one polyazole having at least one amino group in a repeat unit, treating the film with the solution comprising the strong acid and the stabilizing reagent, the total content of stabilizing reagents, performing the stabilization reaction in the membrane directly or in a subsequent membrane processing step, by heating to greater than 25 degrees C and optionally additionally doping the membrane with a strong acid or concentrating the strong acid present by removing water present or producing a solution or dispersion of at least one polyazole having at least one amino group in a repeat unit in orthophosphoric acid and/or polyphosphoric acid, mixing the solution or dispersion with a solution comprising the strong acid and the stabilizing reagent, performing the stabilization reaction in the solution or dispersion directly or in a subsequent processing step, by heating to greater than 25 degrees C and optionally additionally doping the polymer with a strong acid or concentrating the strong acid present by removing water present. Preferred Components: The polyazole has a molecular weight (measured as the intrinsic viscosity) of at least 1.8 dl/g. The polyvinyl alcohol comprises (in wt.%, based on the total weight): substituted vinyl hydroxy repeating unit of formula (-(CH(OH)-CH(R1))-) (I) (1-99); substituted vinyl carboxy repeating unit of formula (-(CH(O-C(=O)-R2)-CH(R1))) (II) (0-99); and substituted vinyl repeating unit of formula (-(C(R5)(R6)-C(R3)(R4))-) (III) (0-70 wt.%). The polyvinyl alcohol comprises (I) and/or (II) (greater than 50 wt.%) or (I) (greater than 50 wt.%). The polyvinyl alcohol has a molar mass of 10000-200000 g/mol.R1 = H or methyl;R2 = H or 1-6C alkyl; andR3-R6 = radicals having molecular weight of 1-500 g/mol. EXAMPLE - 1-5 wt.% Solution (800 ml) of polyvinyl alcohol in 50-85 wt.% phosphoric acid was prepared. A piece of A5 size of a standard polyazole membrane with a thickness of 350 mu m, phosphoric acid concentration of 50 wt.% and solids content of polyazole (5 wt.%) was added to the solution of orthophosphoric acid, heated to 60 degrees C with polyvinyl alcohol (1-5 wt.%). The residence time in the solution was 1 hour. The membrane was subsequently removed from the solution and treated between 2 support materials preferably between 120-160 degrees C in an oven for 1 hour. After stabilization has been performed, the membrane was placed into 50% phosphoric acid for 15-30 minutes.