Surface preparation for electrolytic inorganic finishes

A method, comprising:

• degreasing a metal substrate;
• performing a first alkaline cleaning on the metal substrate;
• etching the metal substrate with an alkaline etchant solution to form an etched metal substrate, the alkaline etchant solution comprising about 2 vol % to about 6 vol % of triethanolamine, about 2 vol % to about 30 vol % of a sodium sulfide additive, about 10 vol % to about 40 vol %, about 75 g/L or less of dissolved metal content, and about 6 g/L or less of ethylenediaminetetraacidic acid (EDTA);
• deoxidizing the etched metal substrate with a deoxidizing solution comprising about 40 vol % to about 60 vol % of nitric acid to form a processed metal substrate;
• performing a second alkaline cleaning on the processed metal substrate;
• optionally performing alkaline etch cleaning with said alkaline etchant and deoxidizing solution comprising about 40 vol % to about 60 vol % of nitric acid, which may be used alone or in combination with iron based or chromated deoxidizing solutions to remove oxides if needed nitric acid deoxidizing solution alone or in combination with other deoxidizing solutions to remove oxides as needed;
• and
• depositing a coating onto the deoxidized metal substrate to form a coated metal substrate.

A method comprising:

• degreasing a metal substrate;
• performing a first alkaline cleaning on the metal substrate;
• etching the metal substrate with an alkaline etchant solution to form an etched metal substrate, the alkaline etchant solution comprising about 2 vol % to about 6 vol % of triethanolamine, about 2 vol % to about 30 vol % of a sodium sulfide additive, about 10 vol % to about 40 vol %, about 75 g/L or less of dissolved metal content, and about 6 g/L or less of ethylenediaminetetraacidic acid (EDTA);
• deoxidizing the etched metal substrate with a deoxidizing solution to form a processed metal substrate, the deoxidizing solution comprising about 40 vol % to about 60 vol % of nitric acid;
• performing a second alkaline cleaning on the processed metal substrate;
• optionally performing alkaline etch cleaning with said alkaline etchant and deoxidizing solution comprising about 40 vol % to about 60 vol % of nitric acid, which may be used alone or in combination with iron based or chromated deoxidizing solutions to remove oxides if needed;
• depositing a coating onto the processed metal substrate to form a coated metal substrate, wherein depositing a coating onto the processed metal substrate comprises electrolytically depositing an inorganic finish thereon, the electrolytic deposition of the inorganic finish comprising:
• attaching the processed metal substrate to two or more counter electrodes,
• electrically connecting the processed metal substrate to a power supply,
• immersing the processed metal substrate within an inorganic finishing solution,
• applying a current density to the processed metal substrate to form a coated metal substrate, and
• rinsing the coated metal substrate.