Method for producing a coating system with an aqueous basecoat

A method for producing a coating system on a substrate, comprising

• producing a cured basecoat film on the substrate by applying a pigmented aqueous basecoat material to the substrate and subsequently curing the basecoat material,
• wherein
• the pigmented aqueous basecoat material comprises a carboxy-functional polyether-based reaction product which is preparable by reaction of
• (a) at least one cyclic tetracarboxylic dianhydride having an aliphatic, aromatic or araliphatic radical X which bridges the two anhydride groups,
• with
• (b) at least one polyether of a general structural formula (II)
• in which
• R is a C3 to C6 alkylene radical and n is selected such that the polyether (b) possesses a number-average molecular weight of 500 to 5000 g/mol,
• wherein components (a) and (b) are used in the reaction in a molar ratio of 0.7/2.3 to 1.6/1.7 and a resulting reaction product possesses an acid number of 5 to 80 mg KOH/g,
• and wherein
• the cured basecoat film represents at least partially the uppermost coat of the coating system produced.