INCONEL® alloy 686 (UNS N06686 / W.Nr. 2.4606) is a single-phase, austenitic Ni-Cr-Mo-W alloy offering outstanding corrosion-resistance in a range of severe environments. Its high nickel (Ni) and molybdenum (Mo) provide good resistance in reducing conditions, and high chromium (Cr) offers resistance to oxidizing media. Molybdenum (Mo) and tungsten (W) aid resistance to localized corrosion such as pitting. Iron (Fe) is closely controlled to enhance properties. Low carbon (C) helps minimize grain boundary precipitation to maintain corrosion-resistance in the heat-affected zones of welded joints. Resistance to general, pitting and crevice corrosion increases with the alloying (Cr+Mo+W) content, and INCONEL alloy 686 scores higher than competitive materials. INCONEL alloy 686 is protected by U.S. patent 5,019,184.

Its matched composition welding products, designated as INCO-WELD® filler metals and welding electrode 686 CPT® also offer exceptional as-welded resistance to sulfuric or hydrochloric acids, to mixtures of the two, and to crevice or pitting corrosion in hot concentrated acid chloride solutions. These welding products are also used for dissimilar and overmatched welding applications.

INCONEL alloy 686 is used for resistance to aggressive media in chemical processing, pollution control, pulp and paper manufacture, and waste management applications.

Corrosion Resistance

INCONEL alloy 686 offers outstanding resistance to general corrosion, to stress-corrosion cracking, and to pitting and crevice corrosion. Its resistance to intergranular precipitation during welding maintains its corrosion-resistance in the heat-affect zones of welded joints.

It offers resistance to both reducing and oxidizing acids and to mixed acid solutions. It is especially suited to handling mixed acids containing high concentrations of halides. It has shown good resistance to mixed acid media with pH levels of 1 or less, and chloride levels of over 100,000 ppm.