| 摘要 |
PURPOSE:To improve the effects of acid pickling and cleaning without the formation of pitting in stainless steel, by adding a specified metal dithiocarbamate to a liquid mixture of nitric and hydrofluoric acids as acid pickling agent for stainless steel. CONSTITUTION:A metal dithiocarbamate represented by formula[I], wherein R1 and R2 are each a hydrogen atom or a 1-7C aliphatic hydrocarbon, monocyclic or polycyclic aromatic hydrocarbon or alycyclic hydrocarbon group, or R1 and R2 are combined together to form a heterocyclic group containing the adjacent nitrogen atom, Me is a metal, and n is its valency, e.g. sodium dimethyl-dithiocarbamate or zinc diethyldithiocarbamate, or a metal dithiocarbamate coupled by a divalent organic group represented by formula[II], wherein R3 is a divalent organic group, R4 and R5 are each a hydrogen atom or a 1-7C aliphatic hydrocarbon, monocyclic or polycyclic aromatic hydrocarbon or alicyclic hydrocarbon group, Me is a metal, and n is its valency, e.g. tin ethylenebisdithiocarbamate or sodium propylenebisdithiocarbamate, is added to a low-temperature liquid of 30-60 deg.C comprising a liquid mixture of nitric and hydrofluoric acids commonly used as acid pickling agent for stainless steel at a proportion of 0.005-10.0wt%. The additive has an excellent acid pickling effect without violently corroding the surface of stainless steel or forming noxious HF gas. |
