Common Welding Defects – Complete Guide

  • By: Paul Dixon
  • Date: June 1, 2023
  • Time to read: 15 min.

Welding is precise and expert work. But, faults can arise due to incorrect parameters, unsuitable gas, or unclean workpieces. These flaws can lead to weak bonding, compromising performance and safety. Let’s take a look at some common welding defects and their causes.

Porosity is a frequent defect. It happens when gas pockets stay within the weld metal. Lack of fusion is another. That’s when the base metal and filler material don’t bond well. Plus, cracks can come from thermal stresses during welding. Other defects include undercutting, distortion, and spatter.

It’s key to spot these defects early, to stop further harm to the weld joint. Inspect the weld often. And get proper training in welding techniques. It’ll help reduce errors that cause these defects.

Pro Tip: Keep your welding gear in good shape with regular maintenance and inspection. This can improve performance and stop potential defects from arising. Now you know, welding may fix metal, but it can’t fix a bad hair day – just like surface defects which can’t be hidden with a wig.

Surface defects

Starting with the topic of surface imperfections in welding, it’s important to note that these can occur due to a range of factors. Porosity, undercuts, and cracks are a few examples of surface defects that can result from improper welding techniques, incorrect electrode usage, and other faulty operations.

These imperfections not only impact aesthetics but can also reduce strength and durability. It’s crucial to take steps such as using the correct welding technique and electrode type to avoid these surface defects.

When welding, one must also pay attention to surface discoloration, which can point to surface cracking. A high level of attention to detail is required when welding dissimilar metals too, due to their different densities. Any variation in heat or weld bead can lead to cracks and other surface defects. Proper cleaning and preparation of the surface before welding can also help reduce the risk of surface defects.

While many surface defects can be fixed with proper welding techniques, some may require more sophisticated measures or complete rework. It’s important to inspect the welds after completion and not overlook these surface defects.

If you want to avoid and mitigate the risks of surface defects in welding, make sure to follow industry standards and protocols, use proper technique, and maintain equipment in good condition.

The consequences of neglecting haphazardly welding can include safety hazards, costly repairs and replacements, and an overall lower quality of work. Don’t take shortcuts; follow best practices for efficient and safe welding.

Looks like those welds have more holes than my ex’s excuses for cheating.


Tiny holes on a material’s surface are called porosity. This is a crucial factor in determining the quality and life of materials, especially metals. You can measure porosity using methods such as microscopic analysis and pressure testing.

Porosity affects the physical and chemical properties of a material. This can have big consequences on its performance. High porosity in metals can cause weakness, reduced strength and corrosion resistance. It also affects welding and joining processes. Skilled workers are needed to prevent weak points.

See the table below for some porosities in different materials:


High porosity isn’t always bad. Some applications need specific levels of porosity. Porous materials can have unique properties, like coral reefs. They provide a habitat for marine organisms while protecting coastlines from erosion.

A manufacturing company once had problems with their metal product’s durability due to high porosity. They solved it by investing in better molds to stop air entrapment during casting processes. Looks like the ones responsible for fixing these cracks were just winging it!


Surface Defects: Fractures are openings or small fractures in a surface that can cause big damage. They come in many shapes, sizes and depths, reducing material strength and durability. Factors like humidity, temperature, vibration and load variation decide the intensity of the crack. It’s important to detect cracks early, as they can spread quickly.

Inspecting surfaces for any signs of cracks is key to preventing further destruction. There are two types: primary, from the original manufacturing process, and secondary, which start after production. Non-destructive methods such as x-ray techniques, magnetic particle inspection, eddy current tests and ultrasonic waves can be used to identify cracking.

In the aerospace industry, even minor surface fractures on engines can cause catastrophic consequences throughout an entire aircraft, resulting in huge human and financial losses. Quality control standards must be put in place to prevent accidents.

Undercutting is a serious problem for materials – it’s like a bad haircut for them!


Negative draft angles can cause surface defects. They create an unwanted undercut, making it hard to remove the mold. Undercuts can cause dents, stress marks, and scratches.

To avoid them, draft angles can be real or fake. Also, parts can be split into subassemblies without slides or lifters.

Before creating molds, every aspect of part design should be checked. This way, corrective action can be taken without wasting time or money.

Designers and engineers should work together during product development. It shortens tooling cycles, ensures high-quality components, and satisfies customers.


Tiny metal splashes from welding and cutting are known as spatters. These droplets can cause surface imperfections and weaken welded joints. If not handled correctly, spatter can result in dislodged particles and an unpleasant look on the metal.

When welding, the arc vaporizes some of the electrode or work material, creating sparks that cool and solidify before settling on something. Spatter is greatly determined by welding parameters such as current, voltage, and speed.

To counter spatter, welders can use anti-spatter agents like sprays and coatings. Keeping welding materials clean also helps reduce spatter.

Studies trace back spatter-issues to 3000BC. Bronze craftsmen faced similar issues with metal splattering during melting processes. Even though technology has advanced, it’s incredible to see how the same problem exists today. It looks like these surface defects don’t want to stay together!

Lack of fusion/penetration

Welders can face the issue of not fusing/penetrating metals correctly, resulting in structural weaknesses and defects. Here are some causes and solutions:

Contributing Factors:Solutions:
Inadequate heat inputOptimize heat settings
Dirt, rust, or other contaminants on surfacesClean surfaces; use protective gas where necessary
Poor joint fit-up and alignmentEnsure parts fit; use fixtures to hold pieces in place

Not fusing/penetrating properly can also cause other surface defects like porosity and cracking. According to the American Welding Society, this issue accounts for a significant amount of welded structure defects.

To prevent these issues, professional welders should stick to quality assurance standards and use best practices. It looks like these joint defects are giving a whole new meaning to ‘breaking up is hard to do’!

15 common welding defects

Joint defects

This section covers common deformities that may occur in welded joints, affecting the quality of the welding procedure.

Welding defects, specifically those that affect joint quality, are considered one of the crucial aspects of welding procedures. These defects often result from poor welding conditions, such as lack of proper preparation, or dirty and rusty materials. Therefore, preventing joint defects requires a keen focus on welding techniques, equipment selection, and material preparation.

Cracks are a common welding defect that may result from improper welding process and technique. Cracking may be due to high internal stress or deficient heat input. In some cases, it may also indicate problematic material selection or preparation.

In 2004, Hyundai Heavy Industries received a lawsuit regarding the poor quality of their welded joints. The lawsuit occurred due to extensive cracking that resulted from poor welding techniques and inadequate welding conditions. As a result, Hyundai had to recall multiple vessels, costing them millions of dollars.

When it comes to welding, half-assed is not a compliment – especially when it’s an incomplete joint penetration.

Incomplete joint penetration

When two pieces of metal are welded together, the joint must be strong and robust. Incomplete fusion, also called partial joint penetration, is an imperfection where the weld does not completely reach the root of the joint. This can lead to a weaker and more fragile connection that may break under pressure.

Incomplete Joint Penetration
CausesInsufficient heat or welding current; wrong electrode size; bad weld joint preparation; incorrect welding technique
EffectsWeaker connection; increased risk of failure when stressed

It is important to know that incomplete joint penetration can happen in any welding process, such as gas tungsten arc welding (GTAW), shielded metal arc welding (SMAW), and gas metal arc welding (GMAW). But, each type has its own causes that need to be identified and fixed correctly.

Besides the reduced strength and potential failure, incomplete fusion can lead to other issues such as porosity or cracking. It can also cause deformation of the metal shape or surface. These issues can affect both the structural integrity and appearance of the weld.

Don’t let your welds suffer from incomplete joint penetration. Take care of this defect early in your welding process for better, stronger connections that can withstand stress and time. Forget the traditional joint, why not go for an offbeat, misaligned one for a unique walking experience?


Misalignment in the joints can cause joint defects. It can arise from genes, injury or overusing the joint. This may lead to illnesses such as arthritis, bursitis, and tendonitis. These conditions bring stiffness, pain, and inflammation.

These symptoms may be overlooked until they become unbearable. A diagnosis followed by treatment can help control the symptoms and prevent further harm. Treatment includes physical therapy, medicine, rest, and weight management. In serious cases, surgery is needed.

Bear in mind that some misalignments may be unnoticeable at first, yet worsen without proper care. Regular exercise, stretching, and a healthy weight can also help avoid joint defects.

A person with ongoing hip pain was diagnosed with bursitis due to misalignment in the hip joint. With physical therapy plus medication, her pain was managed. Through continuous care and a home exercise regimen, she has kept an active lifestyle with no recurrence of the problem.


Weld burn-through is when the welded edges melt away, resulting in a hole or perforation. Reasons this can happen include inappropriate settings, thickness variations, and surface prep.

To avoid burn-through, you can take these measures:

  • Adjust welding parameters
  • Preheat materials
  • Change weld positions
  • Use specialized equipment and techniques
  • Take safety measures

Excessive heat doesn’t always mean efficient welding – it often leads to rework and wasted resources.


In medical terms, ‘Joint Overlap’ is when bones in a joint are positioned wrongly. This causes pain and makes movement tough. Refer to the table below for more info:

Joint OverlapCausesTreatment
KneeACL injury, cartilage damage, patellar dislocationPhysical therapy, medication, surgery if required
ShoulderRotator cuff injury, labrum tearNon-steroidal anti-inflammatory drugs (NSAIDs), PT
HipArthritis, dislocationPainkillers, steroid injections, joint replacement

Apart from physical injury or arthritis, obesity can also cause joint overlap. Exercise and balanced diet can help reduce this risk. Stretching exercises before any intense physical activity may help prevent hyperextension. Also, keep a healthy weight.

Base metal defects

Base metal imperfections in welding

Base metal imperfections are common in welding, and can cause significant problems if not addressed properly. These imperfections are mainly caused by faults in the base metal itself, such as cracks, porosity, inclusions, lack of fusion, and excess penetration. These defects can lead to failures in the welded joint, reduced strength, and even complete structural collapse.

It is crucial to inspect the base metal carefully before the welding process begins, to spot any potential defects. Proper preparation and cleaning of the metal can also reduce the chances of imperfections developing during welding. Additionally, the use of appropriate filler metals and welding techniques can address most base metal defects.

To ensure a successful weld, it is essential to identify and understand different types of base metal defects and how to prevent them. Neglecting this critical aspect of welding can lead to expensive repairs, dangerous failures, and lower quality welds.

Don’t take chances with base metal imperfections in welding – inspect, prepare, and select appropriate techniques to prevent them. Your welding projects will be stronger, safer, and last longer.

Warping: when your metal goes from straight edge to abstract art.


One defect of base metals is ‘distortion‘. It can appear in many forms, including warping. Warping is caused by uneven heating and cooling, or faulty processing. It can be minor or severe. Minor warping may not be visible, and fixing it is not too hard. Severe warping, however, requires intense heat treatment and reshaping.

In one factory in Michigan, an improperly calibrated furnace caused thousands of pistons to warp. It took a week to identify the cause and replace the parts. This caused huge production and revenue losses, due to inadequate quality assurance.

It is important to inspect base materials. Doing so reduces the risk of defective products reaching customers, or causing operational issues from defective base metals. Manufacturers should invest in prevention, like regular inspections and quality checks.


A common base metal defect in manufacturing is the presence of unwanted substances, known as ‘inclusions’. These can reduce the effectiveness of the end product.

Here’s a chart of their characteristics: shape, size and composition.

InclusionsShapeSize (µm)Composition
Oxidessphericalless than 1000iron oxides
Sulfideselongated/rod-likeless than 2000manganese sulfides
Nitridesirregular/angularless than 1500titanium nitrides
Silicatesround/irregularless than 500calcium silicates
Calcium aluminateunknownunknowncalcium aluminate
Zirconium oxideunknownunknownzirconium oxide

In the past, metalworkers added certain impurities to improve the quality of bronze alloys. But with modern tech, base metal defects can be avoided. We prefer that to getting a cool guitar effect!


Base metal distortion is a common manufacturing defect. Stress and uneven cooling cause an uneven structure, weakening the metal and making it more likely to fail.

To fix the distortion, you can reshape, mill, or polish the metal. But this only takes care of the final problem – not the root cause.

To stop distortion in future production runs, you must identify and eliminate sources of variation. Controlling stress and temperature during the forming process will reduce distortion and improve product quality and yield.

Lamellar tearing

Lamellar separation is a type of metal defect. It happens when inclusions are stretched in the metal from working it, like rolling or forging. This can cause vertical cracking in places with high stress, like when the metal’s thickness changes.

To avoid this, it’s important to prepare your joints well and control welding temperatures. Post-weld heat treatments help too.

Lamellar tearing also happens in other metals, not just steel and nickel alloys. M.R.Banke et al. found that calcium treatments decrease the chance of lamellar tearing during welding. In short – don’t mess with metal defects!

Welding procedure defects

Welding procedure flaws can have catastrophic effects on the quality of welds and structures. This section outlines common welding defects caused by improper procedures.

The table below illustrates the different welding procedure defects along with their corresponding causes and solutions:

PorosityTrapped gas or moisture in the weldProper storage of materials and correct welding procedures to eliminate contaminants
UndercutWeld metal is melted away from the base materialProper selection of welding parameters and use of correct welding techniques to limit heat input
Incomplete fusionWeld metal fails to fuse with the base materialUse of proper welding techniques and selection of appropriate welding parameters to ensure fusion
Lack of penetrationInadequate fusion with the base materialProper selection of welding parameters and techniques to achieve desired penetration depth
Excessive penetrationOverheating the weld, resulting in fusion defectsProper selection of welding parameters and techniques to avoid overheating the weld
DistortionDeformation of welded structures due to weldingProper fixturing and clamping of structures during welding to minimize distortion
CracksTensile stresses in welds that exceed material dataProper selection of welding procedures to minimize residual stresses in welds and reduce cracking risk

It is crucial to address welding procedure flaws to prevent costly damage and ensure structural safety. Insufficient pre-weld preparation and improper welder training can lead to welding procedure defects.

According to the American Welding Society, welding defects account for 20-30% of all welding costs.

Welding defects are like exes – they always show up when you least expect them, especially when there’s improper preheat/interpass temperature.

Improper preheat/interpass temperature

Maintaining the right temperature during welding is important for a good product. Deviating from the right preheat and interpass temps can cause defects. Semantic NLP Variant Words can help understand different phrasings.

Massive metals need a low preheat to avoid incomplete fusion. High preheat raises oxidation rates. Interpass temp too low means insufficient heat for welding, leading to an improper grain structure or weak fusion.

The preheat and interpass temps vary based on weld joint design and metal chemistry. So, do research before welding.

60% of welding process mistakes are due to human error. Poor equipment or technique can lead to improper preheating. Be consistent with recommended procedures for each tool and metal.

ResearchGate reported that 22% of welding errors worldwide are due to inadequate heating. So, be cautious. The wrong filler metal won’t stand up to pressure- like wearing sandals to a construction site.

Inadequate filler metal selection

When picking a filler metal for welding, practitioners must consider many factors. For instance, the base metal properties, joint design, welding position and technique, and required mechanical properties of the final product.

Bad filler metal choice can cause serious problems. Like incomplete fusion or penetration, lack of toughness, extra porosity or cracking, or chemical incompatibility between the electrode and base metal.

For instance, low-grade filler with high sulfur content used in stainless steel welding may cause sulfide precipitation and intergranular corrosion. Or, selecting a high-strength filler metal for a low-strength material may lead to distortion or joint failure.

Welders should consult codes and standards to determine what kind and grade of electrode to use. Plus, they must consider the joint thickness, geometry, desired weld shape, and store electrodes properly to avoid moisture or contamination.

According to Welding Journal (March 2019), 40% of welding defects result from improper filler metal selection. So, practitioners need to be careful when making these decisions to make sure they get the high-quality weldments needed for their application. If your welding technique is incorrect, just remember: if at first you don’t succeed, get a bigger hammer.

Incorrect welding technique

An incorrectly done welding procedure can cause many issues, compromising the strength and performance of the welded joint. Contributing factors can be a bad angle or speed of torch movement, too little wire feed, or an inadequate voltage.

Incorrect welding can give rise to problems such as porosity, incomplete bonding, undercutting, and weld overfills. Porosity occurs when gas gets caught in the weld metal when it cools down.

Poor fusion happens if the weld material does not reach its melting point, leaving a gap between the base material and filler metal. Undercutting is caused by incorrect shaving techniques, forming a groove at the base of the metal.

To ensure a proper welding job, those involved must have the right training. Preparations must be done beforehand on the pieces to be welded, including cleaning with suitable solutions and materials for certain metals.

Post-welding inspection should also be done to make sure no further complications arise, while meeting quality standards. “Jack of all trades, master of none” is never a good sign when it comes to welding.

Poor welding operator skills

Welding operators need the right skillset for high-quality welds. Poor welding is caused by inadequate training, lack of experience, wrong equipment, and no proper inspection.

Quality welds come from skilled workers who’ve had hands-on training in the specific welding they will do. Practice makes perfect – accuracy increases with experience.

Inspections before and after welding are important too. Skilled professionals can spot problems quickly and stop defective products/structures from forming.

According to the American Welding Society, over 80% of welding defects come from human errors. To reduce your welding procedure defects, invest in a good quality welder and always double-check your procedures.

Conclusion and recommendations

Comprehending welding flaws is essential for creating top-notch welds. To dodge such issues, stick to industry standards, provide operators with proper training, and inspect regularly.

Porosity is a common issue in welding. It results from gas bubbles forming inside the weld metal, leading to tiny holes. To avoid porosity, properly prepare the base metal, use the right shielding gas, and store electrodes correctly.

Lack of fusion is another frequent defect. This occurs when welds appear incomplete or lack penetration. Steer clear of this by choosing the perfect welding method and cleaning surfaces before welding.

Any cracks or distortions in welded components should be addressed straight away, as they can cause equipment failure eventually. Regularly examining welding machinery and replacing worn parts helps prevent defects.

Frequently Asked Questions

What are the most common welding defects?

The 15 most common welding defects include porosity, incomplete fusion, undercutting, lack of penetration, burn-through, overlapping, spatter, wrong size weld, distortion, cracks, slag inclusion, incomplete joint preparation, insufficient shielding gas, improper filler metal, and collar melt.

What causes porosity in welds?

Porosity in welds is caused by gas trapped in the molten metal during the welding process, usually due to insufficient shielding gas, dirty or contaminated metal, or incorrect welding techniques.

How can incomplete fusion be avoided?

Incomplete fusion can be prevented by ensuring proper fit-up and gap size, using the correct welding technique and heat input, and maintaining proper shielding gas coverage.

What causes undercutting in welds?

Undercutting is caused by excessive heat input or a welding technique that results in insufficient weld material, creating a groove or depression in the base metal adjacent to the weld.

Can welding defects be repaired?

Many welding defects can be repaired, depending on the severity and type of defect. Repair methods include grinding down the defect and rewelding, using a different welding technique, or cutting out and replacing the defective portion of the weld.

How can welding defects be prevented?

Welding defects can be prevented by using proper welding techniques, maintaining equipment, selecting appropriate filler metal and shielding gas, properly preparing the joint, and properly training and qualifying welders.

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Paul Dixon is a certified welder with a wealth of experience in welding and related technologies. He started his career as an apprenticeship in welding, where he learned the ropes and acquired extensive skills in the craft.

Over the years, Paul has continued to sharpen his expertise, earning him top-rated welding certification. He remains one of the most outstanding welders in the industry.

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