Coating installations are provided that include storage tanks for an aqueous base component and a non-aqueous hardener component, circulation lines for the components from the respective storage tanks, a mixer and an entrance to the mixer with a connection between each circulating line and the entrance to the mixer, and a release valve for the non-aqueous hardener component. The coating installation downstream of the non-aqueous hardener release valve is filled with a non-aqueous solvent composition comprising 0 to 10 wt. % of N-alkyl pyrrolidone, 0 to 5 wt. % of dimethyl sulfoxide, 10 to 50 wt. % of γ-butyrolactone, 10 to 50 wt. % of at least one monoalcohol, 10 to 60 wt. % of at least one organic solvent inert towards isocyanate groups, other than γ-butyrolactone, other than N-alkyl pyrrolidone, and consisting of carbon, hydrogen, oxygen and, optionally, nitrogen, and 0 to 10 wt. % of at least one additive.