>Hi > >Please could you help me regarding welding the stainless >steel 410 with Monel at the crude unit column. Is there is a >possibility of galvanic corrosion > >Moreover, I was confused is the ss410 suitable inside column >I mean it is good to have SS410 tray inside the column. Is >ss410 attacked by the chloride stress cracking? > > Thanks >Corrosion Engineer Mark, Austenitic filler metals are widely used when welding 410 stainless. Austenitic filler metals have a lower shrinkage stress due a lower coefficient of thermal expansion and increased ductility. As well, austenitic structure is not susceptible to hydrogen cracking because hydrogen isn’t soluble in the austenitic lattice structure; 410 stainless are. Monel filler metal is not commonly used to weld 410 SS to itself, NiCrFe-2 or 3 are (especially making repairs to 410 SS cladding). Regarding galvanic corrosion, I wouldn’t expect this type of corrosion in the crude column. Galvanic corrosion requires an electrolyte (crude is not a good electrolyte) to be present; the crude column operates at a high enough temperature to eliminate this. Galvanic corrosion is generally seen in refineries in cooling water systems. General types of corrosion you may see in the crude column would be sulfidation and naphthenic acid attack (if you are refining crude that comes from a region where naphthenic acid is and issue). Sulfidation generally seen in the lower half of the crude column, 410 SS is adequate protection. However, if naphthenic acid is an issue, 410 SS has no or little benefit over carbon steel. An alloy with higher molybdenum and chrome content like 316 or 317 SS would be my choice. In the upper half of the crude column you may see degradation by Hydrochloric acid attack. Alloy 400 (monel) has been used to protect the upper half of the crude column, but expensive. Monel has good resistance to hydrochloric and naphthenic acid attack not so good for sulfidation as nickel alloys don’t resist attack by sulfur compounds. If you are joining Alloy 400 to 410 SS (P6-P42) I would use NiCu-7 welding electrode. Mark, can I ask what refinery do you work or what part of the world do you work???? Good luck!! Scott