General Welding Consumables

Cast iron and dissimilar-metal rods

Nickel-based rods for cast iron engine blocks and pump casings, bronze rods for joining steel to copper-alloy fittings, kept in small quantity because the jobs are rare but the base metal cannot be repaired any other way.

TIG tungsten and flux

Thoriated, ceriated or lanthanated tungsten electrodes ground to the process in use, plus the flux and backing gas needed to keep a root pass clean on stainless pipe.

Shielding and purging gas

Argon, argon-CO2 mixes and pure CO2 cylinders, plus the regulators and flow meters that go with them; gas choice changes penetration and spatter as much as the wire does.

Selection

Match filler to base metal grade first, process second. A wrong filler on a pressure part - a boiler tube, a fuel line, a class-surveyed structural member - can pass a visual inspection and still fail the service it was meant for.

• Base metal certificate or plate marking, not assumption, decides the filler grade
• Diameter matched to plate thickness and position, since overhead work needs a smaller diameter and lower current
• Gas purity and mix matched to the process, especially for stainless root passes where oxygen contamination shows as sugaring on the back of the weld
• Storage condition, since basic-coated stick electrodes pick up moisture and must be held in a heated oven once opened

Regulations and handling

Any repair on a pressure part, a tank boundary or class-surveyed structure needs a hot work permit and, for anything structural, sign-off against a qualified welding procedure. Gas cylinders are carried and stowed under the ship's dangerous goods rules, secured upright, valves protected, and kept away from the consumable store's electrode ovens.

Typical faults

What to look for in a supplier

• Certificates of conformity per batch, traceable to the base material specification
• Consistent packaging that keeps basic-coated electrodes sealed until the oven
• A range wide enough to cover stainless, aluminium and cast iron in small pack sizes, since ship's stock cannot hold a full mill order of each
• Gas cylinder exchange or refill arrangements at the ports the vessel actually calls

Never substitute a mild steel rod because it is what is in the locker - a duplex stainless repair welded with the wrong filler often looks sound and fails by pitting corrosion within months.