If it is difficult to coat then we should try to keep the weld and base metal junctions relatively dry . That is why in most of the welding of CS with SS weld donot show very serious galvanic corrosion in normal ambient condition as the normal moisture in air cannot create a strong electrolyte , But in seaside or offshore structures the humidity is more and air contains more chlorides than normal main land air. Such air will quickly make a conductive electrolyte in joint and galvanic corrosion will happen.