ER5356 Aluminum TIG Filler: High-Strength Marine Grade

ER5356 is the high-strength aluminum TIG filler, and it’s the default choice for welding 5xxx-series marine alloys, structural 6061, and any aluminum part that will be anodized. Its 5% magnesium content delivers about 40% higher tensile strength than ER4043 in the as-welded condition. If you’re building boat hulls, structural frames, pressure vessels, or anything that needs maximum weld strength on aluminum, ER5356 is the rod to reach for.

The wire is classified under AWS A5.10/A5.10M. It deposits a weld with 35,000-40,000 PSI tensile strength, good corrosion resistance in saltwater environments, and an anodized appearance that closely matches most base aluminum alloys.

AWS A5.10 Classification

• E = Electrode
• R = Rod (TIG filler)
• 5356 = Alloy designation (Al-5Mg)

The 5xxx series designates aluminum-magnesium alloys. Magnesium provides solid-solution strengthening (it dissolves into the aluminum matrix and distorts the crystal lattice, making it harder for dislocations to move). This is different from the silicon in ER4043, which primarily improves fluidity rather than strength.

Chemical Composition

Notice the silicon is held to 0.25% max. This is intentional. In Al-Mg alloys, excess silicon combines with magnesium to form Mg2Si, a brittle intermetallic compound that concentrates at grain boundaries and causes cracking. Keeping silicon low protects the ductility and toughness of the deposit.

The chromium and manganese additions improve corrosion resistance, particularly in marine environments where chloride exposure is continuous. This is why 5356 is specified for boat building and offshore structural work.

Mechanical Properties

The shear strength difference is the number that matters most for fillet welds. Fillet welds on aluminum fail in shear, and ER5356’s 20,000+ PSI shear strength provides a significant margin over ER4043’s 15,000-17,000 PSI. For structural work governed by the Aluminum Design Manual or AWS D1.2, this strength advantage often determines the required weld size.

ER5356 vs. ER4043: Complete Comparison

This is the most common filler rod decision in aluminum TIG welding. Both work on 6061 and other popular alloys, but they’re optimized for different priorities.

Strength: ER5356 wins by about 40% in tensile and shear. For structural applications, code-governed joints, and anything subject to dynamic loads, 5356 is the stronger choice.

Crack resistance: ER4043 wins. Silicon widens the solidification range and keeps the weld pool fluid longer, which heals incipient cracks during solidification. ER5356 has a narrower freezing range and is more sensitive to restraint, fit-up gaps, and high-dilution joints. If you’re getting cracks with 5356, try 4043.

Fluidity: ER4043 flows better. The silicon content lowers surface tension and produces a wetter, more spreadable bead. ER5356 runs stiffer and less fluid, which can be an advantage for out-of-position work but makes flat fillet welds less smooth.

Anodizing: ER5356 wins significantly. Its deposit anodizes to a near-match of most base aluminum alloys. ER4043 anodizes dark gray to black, which is unacceptable for architectural and decorative work.

Corrosion resistance: ER5356 has better resistance to saltwater and marine environments. The magnesium and chromium content contributes to a more stable passive oxide layer. ER4043 is adequate for freshwater and indoor use but isn’t the best choice for continuous saltwater exposure.

Casting repairs: ER4043 wins. Most casting alloys contain high silicon, and adding magnesium-rich 5356 filler creates brittle Mg2Si phases. Never use ER5356 on high-silicon casting alloys.

Cost: Roughly equivalent. Both are commodity aluminum fillers available from all major manufacturers.

Base Metal Compatibility

Preferred base metals for ER5356:

• 5052 (sheet, marine, pressure vessels)
• 5083 (marine plate, structural)
• 5086 (marine, unfired pressure vessels)
• 5454 (elevated temperature service)
• 5456 (marine, high-strength plate)
• 6061 (structural extrusions, plate)
• 6063 (architectural extrusions)

Not recommended for:

• Casting alloys (A356, 319, 413) with high silicon content
• 2xxx-series alloys (2024, 2219)
• 7xxx-series alloys (generally not fusion-weldable)
• Pure aluminum (1100, 1350) where ER4043 or ER1100 is preferred

The critical rule: don’t put ER5356 on high-silicon castings. The magnesium-silicon reaction creates Mg2Si at grain boundaries, causing cracking and brittle joints. If you’re unsure about a casting’s composition, default to ER4043.

Marine Applications

ER5356 is the standard filler for marine aluminum construction. Boat hulls, structural components, fuel tanks, and deck fittings built from 5083 or 5086 plate all get welded with 5356 (or its higher-magnesium cousin ER5183 for maximum strength on 5083).

Marine requirements that make ER5356 the right choice:

• Saltwater corrosion resistance: The Al-Mg system forms a stable oxide layer that resists chloride attack
• Fatigue strength: Marine structures see constant cyclic loading from waves, and ER5356’s higher base strength translates to better fatigue performance
• Code compliance: AWS D1.2 and classification society rules (ABS, Lloyd’s, DNV) approve ER5356 for marine structural welding
• No post-weld heat treatment needed: The 5xxx-series alloys and ER5356 achieve their properties in the as-welded condition

For fuel tanks, ER5356 on 5052 or 5083 is the standard combination. The welds must be leak-tested and often radiographed. ER5356’s low porosity tendency on properly cleaned base metal makes it reliable for these critical joints.

Diameter Selection

ER5356 feeds and melts similarly to ER4043 at the same diameter and amperage. The main difference is in puddle behavior: ER5356 is slightly less fluid, so you may need to increase amperage by 5-10% compared to ER4043 settings on the same joint to achieve similar wetting and flow.

Welding Technique

ER5356 requires more attention to cleanliness than ER4043. Magnesium is more reactive than silicon, and any moisture, oil, or oxide contamination on the rod or base metal shows up as porosity.

Joint preparation: Wire-brush with a stainless steel brush immediately before welding. Remove all anodizing, paint, and heavy oxide in the weld zone plus 1 inch on each side. Acetone or MEK for degreasing. Don’t use chlorinated solvents near aluminum welding.

Preheat: Same guidelines as ER4043. Under 1/8" thick needs no preheat. Over 1/4" benefits from 200-300F (93-150C). Don’t exceed 350F on 6061-T6.

Travel speed: ER5356 is more crack-sensitive than ER4043, and slow travel speed increases heat input and restraint. Keep the puddle moving at a steady pace. Avoid stop-start cycles when possible, as crater cracks are common in Al-Mg deposits.

Crater fill: Always fill craters at the end of each weld pass. ER5356 is prone to crater cracking because the high-magnesium deposit contracts sharply during the final solidification. Use your machine’s crater fill function (4T mode or foot pedal ramp-down) to taper amperage at the end of each pass. If crater cracks still appear, add a small extra dab of filler as you ramp off.

Multi-pass welds: Clean each pass with a stainless brush before depositing the next one. Magnesium oxide (the black soot that forms on the surface) traps gas and creates inclusions if welded over.

Shielding Gas

Pure argon at 20-30 CFH is standard. For thick sections (over 3/8"), an argon-helium blend (75/25 or 50/50) increases heat input and helps maintain the puddle on heavy plate. Helium blends cost more and produce a less stable arc, so only use them when pure argon can’t keep up with the thermal demand.

Back-purge on enclosed joints (pipe, tube, sealed boxes) with argon to prevent root-side oxidation. Flow 5-10 CFH through the enclosed area.

Storage and Handling

ER5356 TIG rod ships in sealed tubes of 36-inch cut lengths. The magnesium content makes this alloy slightly more oxidation-prone than ER4043 in humid conditions. Store in a dry environment and reseal tubes after opening.

Handle with clean gloves. The rod surface should appear shiny and silver. If rods develop a dull, white, powdery appearance, the magnesium is oxidizing and the rods will produce porosity. Light surface oxide is unavoidable and burns off in the arc, but heavy oxide warrants replacing the rod.

Common Brands

ER5356 is available from the same manufacturers that produce ER4043:

• Lincoln Electric: SuperGlaze 5356
• Alcotec: ER5356 (the aluminum specialist)
• ESAB: OK Autrod 5356
• Hobart: ER5356 (retail packaging)
• Blue Demon: ER5356

Pricing runs comparable to ER4043 at $12-20 per pound for 36-inch cut lengths. For marine work, buy from a supplier that provides material test reports (MTR) documenting the actual chemical analysis of each production lot. This is required for classification society (ABS, Lloyd’s, DNV) compliance on vessel construction.

For the alternative aluminum filler option, see the ER4043 aluminum TIG filler guide. For general filler rod selection, check the TIG filler rod selection guide.