Good Weld vs Bad Weld : Visible Tests Guide

So you have just started with welding and worried about what a good weld looks likes? In this article we are going to tell how to differentiate a good weld vs bad weld.

Well, every amateur welder has this question in his/her mind when getting started. This very skill of identifying good weld vs a bad weld is very valuable.

This is particularly important if you are working in the food industry or any other industry which has high safety standards and quality regulations.

Old Man finds it hard to differentiate between good weld vs bad weld

Any guide won’t help you, to magically become a professional welder.

Practicing is the best way to get this knowledge and will help you greatly to identify between a good weld and a bad weld.

There’s a lot of things that can make a weld good or bad like cracks, lack of fusion, lack of penetration.

Mostly it’s about penetration, it’s basically how good you are at melting the welding rod with your work material.

Welding Issues that may lead to bad weld!

1. Weld Porosity 

 Weld Porosity is mainly caused when the base metal is either covered in rust, oil, or paint. The presence of those materials on the surface prevents proper penetration and hence results in a bad weld.

To prevent this, one should use a deoxidizer in the wire-like silicon, aluminum. Also, it must be made sure the gas flow of the shielding gas is in the range of 30 to 40 cubic feet per hour.

Typically these types of issues occur in Wire Feed Welding otherwise known as MIG(Metal Inert Gas) welding or GMAW(Gas Metal Arc Welding).

2. Lack of Fusion 

Incomplete fusion or Lack of Fusion is another common problem that occurs between the base metals and the weld beads. 

When the temperature of the base metal is not elevated up to its melting point, leads to Incomplete fusion. This is mainly caused by welding at an incorrect angle which doesn’t distribute heat uniformly.

3. Spatter

A Weld Spatter is small molten metals globs that stick onto anything as they are liquefied. If they land on you, they’ll burn your skin. If they land on your work, it’ll be quite a hassle to get it off it. 

Spatter can be caused due to a number of reasons like metal composition, low-quality filler, welding machine settings, and even the welding technique itself.

A common solution for all the problems there is welding tapes and anti-spatter sprays available. It’s pretty cheap and does its work very well.

As a replacement, you can even use your usual kitchen spray to tackle weld-spatter problems. 

This is the number one culprit of a bad weld. And generally occurs in all types of welding i.e. Mig Welding, TIG Welding, Stick Welding, Oxy Welding, etc

4. Undercutting

Undercutting in welding is the condition when the base metal or material is melted away where the next weld bead is to be deposited and thus results in a sharp nook.

There’s also another condition of undercutting in which the thickness of the base metal is reduced significantly at the line where the weld bead on the final layer of weld metal ties into the surface of the base metal

5. Insufficient penetration

When the base metal is not sufficiently filled to the root of the weld metal and thus doesn’t extend through the joint thickness.

This type of weld discontinuities can be prevented with the help of correct joint design. 

6. Lack of Uniformity

The presence of several irregularities throughout the profile is another common weld discontinuity.

The weld bead should be laid out uniformly. Un-inform weld may lead to a weaker bond and may affect in the long run of the welded component.

Ideally, a weld should have a flat to little convexity.

7. Cracking 

Cracking is considered the direst of all the weld discontinuities because this is doesn’t depend upon the welding machine or the welding technique.

Cracking is associated with the physical nature of the weld metal. Chemical tests are carried out to test whether the particular material is crack-sensitive.

It is mainly classified into two types  :

  • Hot Cracking – Caused due to high temperatures, or when the weld metal is in a solidifying state
  • Cold Cracking – These are caused after the weld metal is solidified. After a certain amount of time crack appears due to stress and thus are also know as delayed crack.

Weld metals are carefully selected for the same reason, and also a handful of procedures like pre-heating, etc are followed to minimize the chances of cracking.

Welding Tests : Detecting and Evaluating Discontinuities

Usually, Welding issues, or as otherwise known as weld discontinuities are often found through visual inspection. However, there are several other inspection methods such as ultrasonics, radiography, etc.

There are other welding tests that are specifically engineered to test the weld quality under different conditions. Some of the testing methods are :

  • X-Ray Testing
  • Magnaflux Tests
  • Dye Penetrant test
  • Fluorescent Penetrant Test
  • Hardness Testing
  • Electromagnetic Tests
  • Acoustic Emission Testing
  • Ferrite Testing
  • Gas Weld Testing
  • Physical Weld Testing
  • Acid Etch Test
  • Guided Bend Test
  • Free Bend Test
  • Hydrostatic Test
  • Magnetic Particle Test
  • Gamma Ray Testing
  • Back Bend Test
  • Nick Break Test
  • Tensile Strength Test

Also, Another very important point to be noted is these discontinuities depend upon the welded code under which the welded component comes under.

Hence the welding inspector who inspects the component determines the quality of a weld based on the welding code and criteria.

Ultrasonic Testing - Good weld vs Bad weld
Ultrasonic Testing of a Welded Steel Pipe

What Makes Up A Good Weld?

If a weld looks bad it doesn’t necessarily mean it’s bad.

You want to make sure that the weld is almost flat on the base metal with a slight convexity. Look out for any molten globs that are left on the base metal. 

If you managed to get everything done right then Ta-da you got yourself a good weld which will have a consistent look throughout time and would hold your project pretty well together.


Learning to spot a good weld from a bad weld will help you immensely with your work.

This skill is greatly appreciated in certain fields such as sanitary welding or speciality welding altogether.

Following the best practices and keeping your equipment in the top-notch form will surely help you.

Don’t forget the safety measures!