The weld metal corrodes much faster than the parent metal, if Type 316L welded with a
matching filler is exposed to hot organic acids. Nine commercial filler metals were evaluated by
preparing welded coupons, and exposing these to different plant environments (with different
organic acid mixtures and temperatures) for several months. The filler metals were chosen to
yield different solidification modes, and to vary chromium, molybdenum and nickel contents.
Only filler metals which are much more highly alloyed than the parent metal gave lower
corrosion rates than the parent metal. Partitioning during and after solidification, and the average alloy content, both affect weld bead corrosion.