Method of controlling oxide scale formation and descaling thereof from metal articles

A process for the manufacture of a stainless steel article comprising hot forming, cold forming and subsequently thermally treating in an oxidizing atmosphere, the process further comprising:

• providing an oxygen content of the atmosphere of at least 3.0% and up to 11%, by volume, to control the oxide scale formed on the steel article;
• immersing the steel article in an electrolyte of an aqueous solution of about 15-25%, by weight, sodium sulfate;
• adjusting and maintaining the electrolyte at a pH of about 2.0 to 3.5 and maintaining at a temperature of 150.degree.-185.degree. F.;
• passing a low density electric current of about 0.1-1.0 A/in.sup.2 through the steel article in the electrolyte to condition the scale for removal;
• removing the steel article from the electrolyte;
• and
• immersing the steel article in an acid solution of less than 10% concentration of an acid selected from the group consisting of nitric and hydrofluoric acid and mixtures thereof to substantially remove the scale.

A process for removing an oxide scale from the surface of a metal article, the process comprising:

• immersing the article in an electrolyte of an aqueous solution of at least one neutral salt from the group consisting of chloride, sulfate and nitrate of an alkali metal or ammonium, the pH of the electrolyte being adjusted to and maintained from about 2.0 to 3.5, the article having an oxide scale equivalent to an oxide scale formed at least in part in an oxidizing atmosphere of at least 3.0% oxygen, by volume;
• passing a low density electric current through the article in the electrolyte to condition the scale for removal;
• and
• removing the article from the electrolyte.

A process for removing an oxide scale from the surface of a stainless steel article, the process comprising:

• immersing an article in an electrolyte of an aqueous solution of about 15-25%, by weight, sodium sulfate, the article having an oxide scale equivalent to an oxide scale formed at least in part in an oxidizing atmosphere of at least 3.0% oxygen, by volume;
• adjusting and maintaining the electrolyte at a pH of about 2.0 and 3.5 and maintaining at a temperature of 150.degree.-185.degree. F.;
• passing a low density electric current of about 0.1-1.0 A/in.sup.2 through the steel article in the electrolyte to condition the scale for removal;
• removing the article from the electrolyte;
• and
• immersing the article in an acid solution of less than 10% concentration of an acid selected from the group consisting of nitric and hydrofluoric acid and mixtures thereof to substantially remove the scale.