Aluminium weld filler selector
Pick the base alloy, joint and service, and get the filler metal to specify — plus the traps that catch people out on 5xxx and 6xxx.
Joint
Section
Matching, not guessing. The filler has to sit close to the base metal in magnesium content for strength and corrosion behaviour, while staying easy enough to run for the joint in hand.
5xxx base → 5xxx filler (ER5183 / ER5356 / ER5556)6xxx base → 4xxx filler (ER4043) to limit hot cracking
| Base alloy | Primary filler | Alternative |
|---|---|---|
| 5083 | ER5183 | ER5356 |
| 5086 | ER5356 | ER5183 |
| 5754 | ER5356 | ER4043 |
| 5052 | ER4043 | ER5356 |
| 5059 | ER5556 | ER5183 |
| 6061 T6 | ER4043 | ER5356 |
- Never use ER4043 on 5083 for structural work — the weld ends up significantly weaker than the plate.
- For 6xxx extrusions, ER4043 limits hot cracking; ER5356 is stronger but more prone to cracking on 6061.
- Buy filler with its own certificate if the vessel is classed — surveyors ask for it.
People also ask
Why not just use ER4043 on everything?
It runs easily but is much lower strength than 5xxx plate, and the weld becomes the weak link. It also anodises to a different colour, which shows on visible joints.
What is the difference between ER5356 and ER5183?
Both are 5% magnesium fillers. ER5183 is the marine-grade specification with tighter impurity limits; ER5356 is more widely available and slightly easier to run.
Does filler choice affect corrosion resistance?
Yes. A 5xxx filler keeps the weld close to the base metal in potential, so the joint behaves like the plate in seawater. Mixing families creates a local anode.
Should I use a backing bar?
For full-penetration butt welds, yes — a removable or permanent 5xxx backing bar gives a clean root and reduces the risk of incomplete fusion.
What about 5083 in H116 for repair welds?
Repairs are common and normal. Keep the heat input controlled and the interpass temperature low; multiple small passes beat one heavy pass.
Can I get filler metal and plate on the same order?
Yes — matching filler, plate and certificates can ship together. See certifications.
Need plate to match these numbers?
Reply in one working day with stock availability and a firm price.
