Quick Answer
Flux core wire can be stored for 1-2 years if kept in proper conditions. The key factors that affect shelf life are moisture, temperature fluctuations, UV light exposure, and physical damage. Storing wire in a sealed plastic bag with desiccant helps prevent moisture damage. Keeping it at moderate temperatures around 70°F avoids issues from heat and cold extremes. Shielding the wire from sunlight prevents UV degradation. Handling it carefully prevents kinks and dents which can weaken the wire over time. With ideal storage conditions, flux core wire lasts 1-2 years before the flux starts to deteriorate.
What is Flux Core Wire?
Flux core wire, also known as gasless MIG wire, is a metal wire filled with flux on the inside. It is used for MIG welding applications where external shielding gas is not required. The flux core contains compounds that produce a protective gas when heated, shielding the weld puddle. Common filler metals used are mild steel, stainless steel, and aluminum. Flux core wire allows welding of thicker metals while portable and outdoors where gas cylinders are inconvenient. The lack of need for external shielding gas makes it popular for DIY and repair work. However, it does not make welds quite as strong and clean as gas-shielded MIG welding.
Key Components
- Metal electrode wire – Typically mild steel, stainless steel, or aluminum.
- Flux core – Powdered compounds that generate protective gas and slag.
- Wire sheath – Thin metal sheath encasing the flux core.
The metal electrode wire provides filler metal for the weld. As it melts, it joins the two base metals being welded. The flux core contains fluoride and silicate compounds along with metal oxides and alloying elements. When heated, these produce gases like CO2 and O2 that shield the weld. The flux also forms a slag which protects the welding as it cools and must be chipped off afterward. The thin wire sheath around the flux holds everything together.
How Does Flux Core Wire Work?
The purpose of the flux core is to provide shielding for the weld so it is protected as it solidifies. Here is how it works:
- As the wire reaches the arc, the heat melts the metal electrode and flux core compounds.
- Chemicals in the flux give off CO2, O2, and other gases that surround the weld, displacing air.
- The gases protect the vulnerable molten weld metal from oxygen which can cause porosity.
- Flux chemicals form slag which floats on top and hardens to seal the weld as it cools.
- The protective slag cracks off when the weld has solidified.
This built-in flux eliminates the need for external shielding gas and slag. However, the protection is not as complete as bottled inert gas like argon or helium. So flux core welds tend to have more spatter and porosity issues. The leftover slag also takes more time to chip off completely.
How to Store Flux Core Wire
To maximize the shelf life of flux core wire, proper storage is crucial. Here are some tips for storing it:
- Keep sealed in original packaging or plastic bags – This prevents moisture absorption which can degrade the flux and alloy materials.
- Put desiccant packs in storage containers – Desiccant beads or bags soak up any moisture that could lead to deterioration.
- Store in cool, dry place – Temperature extremes and humidity can accelerate breakdown of flux.
- Avoid direct sunlight – UV rays can damage wire coatings and welding properties over time.
- Keep free of dust and dirt – Contamination can get embedded in the wire surface and cause welding defects.
- Avoid crushing, kinking, bending – Physical damage makes wire harder to feed smoothly.
The cleaner and drier you keep the storage environment, the better. Try to keep temperatures reasonably stable around 70°F. Letting wire get hot and cold leads to expansion and contraction that strains the wire.
Ideal Storage Container
The best way to store MIG wire is in an airtight plastic bag or container with desiccant. Here are recommended storage containers:
- Original wire spool packaging – Moisture-proof plastic packaging.
- Vacuum sealed bags – Press out air and seal to prevent moisture and oxidation.
- Plastic cases with gasket seals – Protects from dust and moisture.
- Metal wire boxes – Durable protection but more prone to humidity.
- 5 gallon plastic buckets – Low cost way to seal out moisture.
For long term storage, vacuum bags or pail are ideal. Reseal any opened spools in plastic bags with desiccant. Try to use wire within 1-2 years for best results.
Effects of Improper Storage
Storing wire improperly leads to issues like:
- Moisture absorption – Leads to flux and alloy corrosion, arcing problems.
- Dust and dirt contamination – Can reduce weld quality and conductivity.
- UV light damage – Embrittles and fades wire coatings over time.
- Crushing and kinking – Makes wire hard to feed smoothly during welding.
- Temperature extremes – Expands and contracts wire leading to fatigue and cracks.
- Flux decomposition – Causes porous, brittle welds with more spatter and fumes.
Storing wire in damp environments or letting moisture directly contact the wire leads to the worst problems. The humidity causes corrosion and degradation of the flux core and alloy materials. But excessive heat, cold, sun exposure, and mishandling also accelerate deterioration.
Signs of Deteriorated Flux Core Wire
Here are signs your stored flux core wire may be past its prime:
- Corrosion on wire surface
- White oxidation powder on surface
- Embrittlement and cracking
- Peeling/fading of wire coating
- Bends and kinks that damage wire
- Weld spatter is excessive
- Weld porosity, weak fusion
- Excessive smoke or odor from flux
If you notice any of these warning signs as you use the wire, it likely means the flux has degraded during storage. Discard any flux core wire that displays these issues and get fresh wire. Trying to use deteriorated wire will lead to very poor weld quality.
What is the Shelf Life of Flux Core Wire?
With proper storage, here are the typical shelf life estimates for flux core wire:
- Sealed in climate-controlled environment – 2 years
- Sealed with desiccant at room temperature – 1-2 years
- Open coil at room temperature – 6-12 months
- Open coil in hot/humid area – less than 6 months
The more you expose the coiled wire to moisture and contamination, the faster the flux will fail. Kept unopened in a controlled storage room, the shelf life can reach 2 years before the flux composition degrades. But opened wire left sitting in a workshop will deteriorate much quicker.
Here are some signs the wire has expired:
- Poor weld appearance and strength
- Arc sputtering and instability
- Excessive spatter and smoke
- Wire jamming in gun or feeder
Once you notice these issues, it means critical components in the flux have broken down. At that point, the degraded wire will lead to very inconsistent and questionable weld quality. Any expired wire should be discarded and replaced with fresh stock for reliable performance.
Does Flux Core Wire Go Bad?
Yes, flux core wire does have a limited shelf life. The flux components inside the wire will eventually degrade and expire. This leads to poor arc performance and lower-quality welds.
Moisture, oxygen, and temperature extremes slowly damage the flux and alloy materials inside over time. While the thin metal wire is fairly stable, the flux core is more prone to deterioration. Once the flux expires past its shelf life, it results in issues like:
- Porosity from poor gas coverage
- Lack of fusion defects
- Excessive spatter and smoke
- Inconsistent weld appearance
- Brittleness and cracking
For best results, flux core wire should be stored carefully and used within 1-2 years. Keeping it in sealed bags or containers with desiccant helps extend its shelf life at room temperature. But expired wire that has been exposed to moisture or other damage should always be replaced with fresh wire.
Does Moisture Affect Flux Core Wire?
Yes, moisture can severely affect the shelf life of flux core wire. The flux inside is hygroscopic, meaning it readily absorbs moisture from the air. Absorbed moisture causes oxidation and corrosion of the flux chemicals and alloy materials inside the wire. This leads to poor performance and weld defects.
Even a small amount of moisture (less than 0.5%) quickly degrades wire after absorption. Lower welding current, lots of spatter, and excessive smoke are signs of a moisture issue. Storing wire in humid conditions for an extended time makes the problem worse.
Always keep flux core wire sealed in plastic or metal containers to prevent moisture absorption. Use desiccant packs inside storage boxes or bags to maintain bone-dry conditions. If storing open spools, wrap tightly with plastic to prevent exposure to humidity in the air. Monitor wire surface for signs of corrosion or white oxidation powder.
Once wire has absorbed moisture, it can be dried using an oven or holding at 250-300°F for an hour or two. But if corrosion is visible, the damage has already occurred and drying will not restore performance. Preventing moisture exposure through proper storage is critical for maximizing the shelf life.
Does Temperature Affect Flux Core Wire?
Yes, temperature extremes and fluctuations can degrade flux core wire over time. The main causes are:
- Expansion and contraction of wire from temperature changes leading to work hardening and cracks.
- Flux chemical breakdown hastened by excessive heat.
- Embrittlement of wire and coatings when frozen.
Storing wire in consistently cool conditions around 70°F is ideal. Allowing it to freeze or get hot accelerates deterioration. Keeping it at stable temperatures avoids fatigue from expansion and contraction stresses.
If using wire that was frozen, allow it to fully reach room temperature before welding to prevent issues feeding the stiff wire. Do not attempt to warm frozen wire quickly, as heating up too fast causes condensation under the wire sheath.
Avoid storing wire in spaces like attics or sheds that see temperature swings from seasons or day/night. Try to keep wire in air conditioned spaces year-round for maximum shelf life.
How to Prevent Flux Core Wire from Going Bad
Here are some tips to prevent premature deterioration of flux core wire:
- Keep sealed in moisture-proof packaging – Blocks humidity absorption into the flux.
- Store in cool, dry place – Minimizes flux chemical breakdown around 70°F.
- Avoid direct sun exposure – Stops UV damage to wire coatings.
- Use with 2 years of manufacture – Prevents long term degradation issues.
- Inspect condition before use – Check for corrosion, fading, kinks.
- Reseal opened spools tightly – Limit moisture and oxygen contact.
- Put desiccant in storage containers – Keeps conditions very dry.
Getting wire quality matched to your specific welding process will also provide maximum shelf life. Buy high-quality wire from reputable brands that use high purity ingredients and good manufacturing/packaging practices. With proper storage and handling, quality flux core wire should provide 1-2 years of shelf life.
Conclusion
Flux core arc welding wire provides the benefits of built-in shielding from the flux core. But it does require more careful storage than solid wire to prevent deterioration issues over time. Keep flux core wire sealed in plastic bags or airtight containers to maximize its 1-2 year shelf life. Well-controlled room temperature around 70°F and very low humidity are ideal for preserving wire. Check for any corrosion, damage, or functionality issues before using wire that has been stored for an extended time. With proper precautions, flux core wire can be stored and used effectively for many welding projects.
