I need to make some modification to an old chemical pressure tank rated at 250 psi. it will be used as an air tank at a working pressure of 125psi.
It is about 5/16th thick  in good shape and rust free. I have been unable to find any recommended procedures or precautions for this material. a welding supply store recommended using rod LH8018C3MR, but that was all the info they had. Anyone having any experience with this alloy?