UREA-CONTAINING ETCHING AGENT AND A METHOD FOR PREPARATION THEREOF Russian patent published in 2005 - IPC

FIELD: chemical treatment of metals.

SUBSTANCE: objective of invention is removal of oxide layer in stainless steel after a heat treatment such as welding. Water-based etching agent contains nitric acid, 15-30%, and filler in the form of powder-like inorganic thickener used in amounts from 2 to 30%. When etching agent has appearance of paste or gel, it should be placed on the surface of thermally treated stainless steel. When etching agent is in a liquid form, it should be sprayed onto surface. In latter case, etching agent also includes urea in amount at least 0.5 g/L (but not more than 200 g/L) in order to reduce formation of nitrogenous vapors when using this etching agent and it is stable in long-time storage at room temperature. Such etching agent is prepared by adding urea when nitric acid (or acids) and filler have temperature below 30°C, preferably below 25°C and preferably in the final preparation stage, when nitric acid (or acids) and filler are already cooled.

EFFECT: increased efficiency, easiness in use, and storage and transportation stability of agent.

10 cl, 4 dwg, 4 tbl, 4 ex