Abstract
Corrosion resistance of diffusion bonded joint with Ta foil inserted between the bonded surfaces and friction welding joint for SUS304L and Zr was examined in 3N-HNO3 solution contained Cr6+ ion.
In a short term dipping test, it was difficult to qualitatively investigate the corrosion property for both joints, because it depended strongly on the surface condition (preparation) of the specimen before the test. In a long term dipping test, however, the type of the corrosion was mainly found intergranular corrosion in SUS304L base metal for all of the joints, moreover this developed the falling off the crystal grain of SUS304L base metal. In this corrosion process, a possibility that galvanic potential difference between dissimilar metals accelerated corrosion was pointed out, then local potential gradient was investigated using a measuring system, in which a sharp vibrating probe was scanned across the joint interface. SUS304L base metal showed a positive local potential gradient which indicated on acceleration of corrosion in SUS304L. But it was not so large and corrosion rates of SUS304L for the both solid state joining were nearly same value as that without Zr or Ta base metals.
The acceleration of the corrosion at dissimilar metal joints were not observed from the results of the dipping test and the measurement of the local potential gradient, it is considered that there is no problem of the corrosion resistance in these joints.
