The invention relates to stabilised or storage-stable compositions, containing: (A) 2.5 to 15 wt.% of isothiazolinones 2-methyl-2H-isothiazolin-3-one and 1,2-benzisothiazolin-one and/or the sodium and/or potassium salts thereof； (B) 0.5 to 50 wt.ppm of copper(II) ions, in relation to the weight portion of component (A)； (C) 100 to 2,500 wt.ppm, in relation to the total composition, of at least one oxidising agent, selected from the group consisting of sodium iodate, potassium iodate, sodium bromate and potassium bromate, or mixtures thereof； and (D) water. The invention also relates to a method for the preservation of technical materials using the above-mentioned compositions, as well as technical materials treated with same.
