How to Detect a Cold Weld

Find out of it's a "hot" or a "cold" weld, and know what you're dealing with.

A hot weld, or weld made with molten metal, is a true weld which joins two materials together, and actually causes them to become one solid unit. A cold "weld" is an adhesive filler which, although fairly strong initially, is not nearly as durable as a true hot weld, nor does it achieve the joining together of the two separate materials as does a hot weld. Detect a cold weld in seconds by using a few common tools and know for certain that the weld you see is the weld you get.

Things You'll Need

• Pocket knife
• Hammer
• Magnet

Instructions

Visual Inspection

1. 

   Inspect the weld to determine its soundness

   Take a look at the weld for obvious signs it is a cold weld, such as cracking, strange odor or fingerprints. The presence of fingerprints in a weld means it was absolutely done as a cold process. Had it been a hot weld, it would have burned the person's fingerprint off the finger.

2. Perform a crack test on the weld in question using a small hammer, such as a tack hammer. Lightly tap the weld. If the weld is a true weld done in the molten state (hot), it will ring with a metallic sound, because it was made with molten metal. If the weld sounds dull, that is a good indicator that it was made of epoxy and resin, the common components of a cold weld.

3. Perform a magnetic test on the weld using a small magnet, such as a telescoping pocket magnet. Typically, if a magnet sticks easily to a weld, it is a true hot weld. If there is a weak attraction, the weld is probably a cold weld. The material in a cold weld tends to act as a barrier for magnetic attraction, thereby causing a weaker magnetic field.

Tips & Warnings

• Ask a qualified welder if you are uncertain about weld verification. Even hot welds can be unsound, especially if there is cracking, small holes that formed when cooling (porosity), or contamination.

• Always use proper eye protective lenses with side shields when tapping welds. Shards may fly from the weld, causing serious and permanent eye injury or possible blindness.

References

• jbweld.com: cold welds
• aws.org: welding inspection
• esabna.com: weld inspection

Resources

• barrelpoint.com: Cold weld dangers