Surface treatment process for polyamide substrates to improve the adherence of organic coatings

摘要

To improve the adherence of organic coatings on polyamide substrates, a surface treatment of the latter is conducted with the aid of a solution, in an organic solvent, of at least one acid of oxidising nature and which does not form any water-soluble compounds either with the treatment mixture or with the substrate. A solution containing approximately 1 to 15 % by weight of the said acid is generally employed. The latter is especially nitric acid, a chromic acid or acetic acid, nitric acid being preferred. A treatment solution containing at least one nonbasic adhesion promoter which is compatible with the acid employed, in a proportion especially of 0.2 to 2 % by weight of the said promoter in relation to the weight of the treatment solution, may be advantageously employed. The adhesion promoter can also be incorporated in the material intended to form the primer or sizing or base coat, being applied onto the substrate treated with the acid of oxidising nature.