K-T Industries Ruby Fluid Stainless Steel Soldering Flux is formulated for soldering stainless steel and other high-chrome alloys. It exhibits excellent capillary action across a broad range of base metals, solders, and temperatures. Water soluble flux allows the flux to be washed away after soldering. Most fluxes stay in the pipe and continue to corrode the inside of the pipe causing premature breakage or pipe wear out.