The Common Types of Visual Welding Defects

Almost every weld has some tiny flaw hiding in it. The real trick is figuring out if that flaw actually matters. Miss a welding defect, and suddenly your gear - or that expensive bit of property - can end up trashed. The earlier you spot a problem, the less of a headache it becomes. Patch it now, skip the drama later.

Most of the time, if there's something wrong, you can actually see it. Surface defects are usually right there - no microscope required. Sometimes it's just sloppy technique, other times the equipment wasn't set up right. And don't forget the misery that cold weather and damp air can bring while you're working - they leave their own marks too.

That said, you're going to need more than a casual glance to really trust a weld. Picking up on every visual defect only happens if you actually know what you're looking at and you stay sharp on the job. Otherwise, stuff slips by. Reliability depends on it.

What Are the Types of Visual Welding Defects?

Here, let's explore the types of visual defects in welding, how they occur, and how to mitigate them.

1. Spatter

Let's talk about spatter. If you've welded before, you know the drill: tiny blobs of metal flung off and stuck all over your weld - and everywhere else nearby. Looks messy, feels annoying, and sure doesn't do your welding cart any favors (or your hands, if you're not careful).

Why does spatter happen? Usually, you're running the current too high, or the weld pool's out of whack - either roasting hot or way too cool. Dirty metal messes it up, too. A huge arc, a soggy electrode, or just a sudden break in the arc can send sparks everywhere. It doesn't take much.

Cutting back on spatter's not rocket science, but it does take prep. Keep the metal bone-dry and spotless - rust, oil, even a little dust, junk it. Your gear should be just as clean. Don't push the current past what's called for; get the arc length right. Going with AC power helps keep things steady, and there's less chance of sputters. And if you're battling stubborn spatter marks, hit them with a steel milling disc. They won't disappear, but they'll look a lot less ugly.

2. Cracks

Weld cracks are pretty much the last thing you want to find in a finished product. They can show up anywhere: right on the surface, buried inside the weld, or lurking in the heat-affected zone around it. Ignore them, and you're playing with disaster - these cracks can bring down the whole structure.

You'll usually run into three kinds:

• Hot cracks: These break out while you're welding, right in the middle of all that heat (we're talking temps over 10,000C).

• Cold cracks: These take their time, sneaking in after everything's cooled down and you thought you were done.

• Crater cracks: The weld crater at the end doesn't always close up the way it should. That's where they show their face, right before you finish the job.

Why do cracks happen? Plenty of reasons:

• Bad design choices from the start

• Using hydrogen as your shielding gas on metals like steel, iron, copper, or lead (big mistake)

• Skipping preheat - just going for it cold

• Residual stress hanging around

• Too much sulfur or carbon in the metal

• Metal that just won't flex enough

• Letting the crater fill badly at the end

If you actually want to avoid cracks (and you do), you've got options:

• Preheat your weld zone, slow down the cooling - don't rush straight in

• Fit the joints so there's less of a gap

• Use the right shielding gas for your material

• Keep your welding speed and current in check (not too wild, not too slow)

• Clean off everything before you start - no shortcuts here

• Make sure it cools down right after you're done

• Don't go overboard with sulfur and carbon

3. Undercut

Undercut - that annoying little groove that forms at the weld toe. You've seen it: it runs right along the edge of the weld, like the weld metal just couldn't quite reach. Besides looking rough (it really does ruin the finish), it can actually mess with the structure. Water, grime, whatever - once it gets trapped in there, good luck.

If the groove's shallow, under 1/32", most folks just shrug it off. Go any deeper, though, and now you've got a problem you can't ignore.

So why does undercut even happen? People love to blame the setup - and usually, they're right:

• Wrong angle on the electrode

• The electrode's too big for the job

• Junk in the shielding gas

• Cranking the current way too high

• Trying to weld at breakneck speed

• Or just holding the arc too far out

Want to avoid it? Pull the arc in - shorter arc length, or drop the voltage a bit. Match your electrode size to what you're welding. Make sure your shielding gas actually fits the metal. The angle matters too; you want it somewhere between that 30° to 45° zone. And honestly, just clean up - nobody gets a good weld on a greasy or shaky setup.

4. Porosity

Porosity means you're dealing with too many holes - gas bubbles, pockets, that kind of mess - stuck inside your weld. It looks ugly, sometimes obvious, and it hits hardest in MIG welds. Cracks jump out at you, and the whole thing's weaker than it's supposed to be.

• Surface porosity: Scattered across the top - literally looks like someone punched holes everywhere. Swiss cheese vibes.

• Subsurface porosity: Buried under the bead, invisible unless you bother with x-rays.

• Wormholing: Stretched out, winding holes-like worms died in there. Gross.

• Cratering: Dents that show up at the ends of your beads, as if something sucked the weld in before it cooled.

But why does this junk happen?

• Metal isn't clean-dirt, rust, oil, whatever; it invites bubbles.

• The electrode coating is wrong for the job.

• Shielding gas isn't right, or maybe there's just way too much gas blasting out.

• The electrode's wet. Moisture means trouble.

How do you stop it?

• Actually, clean the stuff you're going to weld. Not kind of, actually.

• Keep wind and drafts down-it screws with the gas shield.

• Use dry, good-quality electrodes. Don't cheap out.

• Dial in the gas flow - too much isn't helping, neither is too little.

5. Overlap

Overlap happens when the weld metal kind of spills over at the edge - covers the base metal but doesn't actually bond. Usually, it's just too much weld metal flooding the area. It's not just messy. You end up with poor fusion, the two pieces don't really stick together, plus you set yourself up for weak spots where stress can pile up and things could go wrong.

Why does this happen? Sloppy welding technique, using the wrong size electrode, amping up the current way too high, or just welding from a weird angle. Basically, it's easy to screw up if you're not paying attention.

If you want to avoid overlap, start with getting your technique sorted, pick an electrode that actually fits the job, and dial in the welding current where it belongs. You stop overlapping at the hand, not after the fact.

6. Distortion

Distortion pops up all the time in welding, especially on thinner plates that can't handle the heat. Instead of neat welds, you get structures that look a little warped or lopsided. Not just ugly, either; distortion messes with how sturdy the whole thing is.

So what's behind all this? Going too slow with the arc doesn't help. Neither does dragging out the process way longer than you need to, or piling on pass after pass. And if you don't actually check your measurements for diameter, things go off track fast.

If you want to keep distortion out of your welds, a couple of things matter: don't pick stainless when a more manageable metal would do, since some metals just demand way more passes. Stick with a steady arc speed. Actually use measuring tools, not just guesswork. Simple, but people skip it all the time.

How to Avoid Visual Defects in Welding?

The best way to avoid visual welding defects is to thoroughly examine before, during, and after the welding process. Here are some steps to follow:

1. Inspect all material before starting the weld. 

2. Utilize clean material and surface. 

3. Ensure all welding codes and standards are deployed. 

4. Check the finishing of the weld. 

5. Use the optimal size of electrodes. 

6. Use a welding toolbox to properly store and carry the welding equipment. 

7. Inspect each weld pass. 

Conclusion

Spotting welding defects isn't just a box to check - skip it, and you're gambling with the backbone of your whole project. Trouble catches up fast: cracks, pits, weird blobs, they all snowball into bigger headaches down the line. That's why we pulled together a rundown of the usual suspects you'll see messing up welds. Cut them down early, and half your problems disappear.

Honestly, most of these issues come from sloppy work or using junky materials. Pay attention. Get your hands (and eyes) on the process. Use the guide above as a reality check - find those problems before your project turns into a pile of scrap.