Formulation for the etching of polymer materials prior to coating of the materials

An acid etching bath formulation comprising an acid and Cr(III) coordination complexes, wherein the acid concentration in the etching bath is from 65 wt. % to 98 wt. %,

• wherein the Cr (III) coordination complexes comprise one or more ligands selected from mono, bi, tri, tetra, penta, hexadentate and bridging ligands that are coordinated to the chromium by an oxygen, sulfur or nitrogen atom or a combination thereof,
• wherein the acid in the etching bath is selected from sulfuric acid, aminosulfuric (sulfamic) acid, phosphoric acid, diphosphoric acid, metaphosphoric acid, polyphosphoric acid, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, benzenesulfonic acid, toluenesulfonic acid, cumenesulfonic acid, alkylbenzenesulfonic acids, monoalkylphosphoric acids, dialkylphosphoric acids, isethionic acid, perchloric acid, chloric acid, nitric acid, trifluoromethanesulfonic acid, trifluoroacetic acid, tetrafluoroboric acid, hexafluorophosphoric acid, hexafluorosilicic acid, hydrofluoric acid, boric acid or mixtures thereof.