Aluminum Welding for Pressure Vessels & Tanks
The welds in storage tanks, tankers and chemical vessels must carry the working pressure, seal the media and remain leak-free and corrosion-resistant over long service. TGM's Al-Mg wires offer batch-to-batch consistent chemistry, smooth feeding and good process tolerance, with common diameters kept in stock — helping general-industry users reliably obtain sound, mechanically qualified welds that pass procedure qualification and NDT.
Why aluminum for pressure vessels & tanks
Aluminum offers a high strength-to-weight ratio; its naturally formed oxide film provides good corrosion resistance, and it shows no ductile-to-brittle transition at low temperature — which is why it is widely used in cryogenic tanks, transport tankers, and chemical and coastal vessels. Compared with steel vessels, aluminum vessels are substantially lighter, can dispense with an additional corrosion-coating step, and remain reliable in deep-cold duty such as LNG and liquid oxygen. For tankers where haulage cost and payload are decisive, the overall benefit of light weight is especially pronounced.
These vessels carry pressure and hold media, so the base metal is typically a 5xxx Al-Mg alloy — commonly 5083, 5086 or 5454. The joint strength and soundness of the weld directly determine whether the vessel passes acceptance. Filler selection is therefore the first step in process design: get it right, and procedure qualification and NDT proceed more smoothly thereafter.
Recommended fillers
For the 5xxx Al-Mg base metals commonly used in vessels and tanks, we mainly recommend the two Al-Mg wires below — both kept in stock and readily reordered. Selection depends on the base-metal grade, the required joint strength, and whether the part is exposed to seawater or salt-spray. Please provide the base-metal grade and service conditions, and our technical team will advise on selection.
ER5183
The highest-strength of the 5xxx Al-Mg wires, with excellent weld tensile properties and good resistance to seawater and salt-spray corrosion. Suited to high-strength base metals such as 5083 and to coastal or pressurized tanks; recommended where higher weld strength is required.
View ER5183 datasheet →All-rounder · great valueER5356
The most widely used and versatile Al-Mg wire, with balanced strength and corrosion resistance, stable feeding and broad base-metal compatibility. Suitable for general tanks, chemical vessels and most 5xxx structures; practically priced and steadily supplied, it is the standard choice for most applications.
View ER5356 datasheet →Selection summary: choose ER5183 for high-strength base metals, seawater contact, or where higher weld strength is required; choose ER5356 for general vessels and most 5xxx work, where it meets requirements at lower cost. Note that for parts in continuous service above ~65°C, high-magnesium (≥3% Mg) welds should be avoided, as sensitization can lead to stress-corrosion cracking.
Welding notes
Vessel welds usually undergo radiographic or ultrasonic inspection. The points below are proven welding-practice essentials; following them helps produce sound, porosity-free welds that pass mechanical testing, whether feeding by hand or by machine.
- Clean the surface thoroughly before welding. Remove the oxide film with a dedicated stainless-steel brush, then degrease with a solvent such as acetone to eliminate oil and moisture. Porosity largely originates from oxide film and oil and water contamination, so this step must not be skipped.
- Control porosity. Shield with high-purity argon, ensuring adequate gas flow and full nozzle coverage, and prevent drafts from disturbing the shielding gas at the arc. Keep the wire dry and clean, and avoid touching it with bare hands before feeding.
- Control interpass temperature in multi-pass welding. Thick-wall tanks usually require multiple passes; keep the interpass temperature in check between passes (generally below ~120°C for Al-Mg) and remove spatter and oxide as you go, avoiding excessive heat input. Overheating reduces both the strength and the corrosion resistance of the weld.
- Stable feeding gives a stable arc. Neatly layer-wound wire with a uniform, consistent diameter pays off across the run: clean payoff, no tangles, no snagging. Paired with a clean liner and matched drive rolls, it delivers a steady arc and even penetration, with fewer stoppages and smoother operation over long continuous welding. Good feedability and reliable supply are exactly the value TGM wire brings to general-industry production.
What gets rejected at inspection — and why porosity is only half the story
Vessel welds are normally examined volumetrically — most often by radiography, and by ultrasonics where the code permits it in place of RT. The acceptance rules treat two families of defect very differently, and it is worth knowing which is which before the film comes back.
Under ASME Section VIII, Division 1, radiographic acceptance is set by UW-51: cracks, lack of penetration and lack of fusion are not accepted at all — a single indication of any of them rejects the weld, with no size allowance to argue about. Rounded indications, meaning porosity, are judged instead against the code’s porosity charts, where both the size of the pores and the way they are grouped matter: a run of individually small pores clustered in a short length can reject even when no single pore is oversized. Ultrasonic examination carries its own acceptance standards (UW-53 with Mandatory Appendix 12), but the same split applies: the crack-like defects carry no allowance.
The practical consequence for an aluminium vessel shop is that porosity attracts most of the attention because it is the most common finding, but a fusion defect is the more expensive one to discover, because there is no acceptable level of it. The two also have different root causes. Porosity is a hydrogen problem — moisture and contamination on the wire, in the joint or in the gas line. Lack of fusion is a heat and oxide problem: aluminium draws heat out of the joint quickly, so at the start of a pass, or wherever heat input is too low for the section, the pool can lie against the sidewall without wetting it. The tenacious oxide film works against fusion at that face, and because aluminium gives almost no colour change as it approaches melting, the welder has little visual warning that it has happened.
Repair welding: the second attempt is not as good as the first
There is no universal limit on how many times an aluminium weld may be repaired. The number allowed at one location is set by the applicable code and by your customer’s specification, and it is worth establishing before the first repair is cut rather than after. What the metallurgy says is that every repair costs something.
Studies of repair welding on 5083 report that repaired welds test lower in tensile strength than the original weld, and that the repair cycle coarsens the grain and enlarges existing defects in the heat-affected zone. Work on repairing cracks in welded 5083 joints found the repair gave little improvement in residual life. A repair restores the radiograph; it does not necessarily restore the joint.
Three things follow on the floor:
- Remove the defect completely before rewelding. Grind out to sound metal and confirm it. Re-melting over a fusion defect or a crack usually reproduces it slightly deeper down.
- Hold the repair to the same thermal discipline as the original. A repair cavity is small and tempting to fill hot, but the interpass limit and heat-input control apply exactly as they do on the production weld.
- If the same seam is rejected twice in the same place, stop repairing and look at the procedure. Repeat rejects at one location are usually a joint-access, fit-up or parameter problem rather than a welder problem.
From indication to cause
A first reading of what an inspection finding usually means on an aluminium vessel, and what to change on the next joint. Acceptance is always judged against the applicable code and your qualified procedure.
| Indication | What it usually is | What to change |
|---|---|---|
| Rounded indications scattered along the weld | Hydrogen porosity from moisture or contamination on the wire, in the joint or in the gas line | Repeat the cleaning and degreasing sequence, purge and check the gas line, and confirm the wire has been stored dry — see the porosity guide |
| Elongated indication running along the groove face | Lack of sidewall fusion: heat input too low for the section, or oxide not removed immediately before welding | Raise heat input or slow travel enough to wet the sidewall, correct the torch angle, and re-clean the groove immediately before each pass |
| Indication along the root of a single-sided joint | Lack of penetration: root gap or root face outside the qualified range, or the root pass run too fast | Correct the fit-up to the WPS; where the design allows, back gouge and add a sealing run |
| Crack at a weld stop or in the crater | Crater cracking — the arc was broken abruptly and the crater left unfilled | Use crater fill or downslope, and back up onto the finished bead before breaking the arc |
| The same location rejected again after repair | A procedure or access problem rather than workmanship | Stop repairing; review joint design, torch access and the qualified parameters for that seam |
Questions on selection? Contact us
If you are unsure between ER5183 and ER5356, or wish to confirm the match with a specific base-metal grade, our selection guide will guide you step by step by base metal, strength and service environment. You are also welcome to contact our technical team directly — with your service details, we will help determine the grade and diameter and provide reference input on WPS direction.
Further reading: for the troubleshooting sequence when porosity appears, pre-weld cleaning practice and shielding-gas checks, see the guide to aluminum weld porosity.
Lock in the wire for your vessel project
Please provide the base-metal grade, wall thickness, service temperature and estimated volume, and we will determine the grade and diameter for your tank or vessel project. Common sizes are supplied from stock with steady lead times and easy reordering; on-site welding support can also be arranged on request.
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