Abstract: Corrosion tests with austenitic stainless steel TIG(tungsten inert-gas) and A-TIG(A:activating) welded joints in boiling nitric acid and sulphuric acid and cupric sulphate solution at room temperature were carried out.The results show that the joints welded with activating flux(A-TIG) have good resistance to acid corrosion at room temperature,and have better resistance to grain boundary corrosion than ordinary TIG welded joints.Chemical analysis shows that the activating flux has the ability to suppress the burning loss of some alloy elements such as Cr and Ni in welding proess which improves the corrosion resistance of the A-TIG welded joint.