TIG welding is a highly used arc welding technique. It is used for welding together metals like stainless steel, aluminum, copper, and sometimes gold. It is favored mostly because of its squeaky-clean procedure and pure finish. But sometimes, for some technical errors, your TIG weld might not end up shiny.
The main cause behind TIG weld losing its glow is oxidation. When oxygen in the air comes in contact with the molten metal, the welding bead absorbs impurities from the environment. Other than oxidation, anomalies like overheating, contamination, excess current, etc. also play a role in this.
Various other reasons cause TIG weld to lose lustrousness. In this article, I will explore 9 reasons your TIG welds aren’t shiny. Plus, I will add some tips for successful TIG welding for beginners. I will also discuss what makes TIG welding different and better than other arc welding techniques. Let’s begin!
9 reasons your TIG weld is losing lustrousness
As I said in the beginning, the main reason is oxidation. Here I will discuss the events that make TIG weld lose its shininess:
1. Oxidation
Oxidation is the first and foremost reason behind the discoloration of TIG welds. Not only TIG welding, but other forms of arc welding also suffer from it. The molten metal can absorb a variety of gases from the atmosphere such as oxygen, hydrogen, and nitrogen. This can cause several problems like porosity which will make the weld dull looking and weak.
Metal in the molten stage is highly reactive. So, during the welding procedure, the molten base metal comes into contact with the air. Oxygen present in the air reacts with the metal and forms oxide. The formation of oxide weakens the joint, creates rust, and discolors the welding. The color becomes gray and a clean outcome of TIG welding is hindered.
Besides discoloring the weld, oxidation also facilitates corrosion. Failure to prevent oxidation shall result in a weak joint and grayish color of the weld.
2. Overheating of the Metal
Elements become highly reactive when heated. Metals are no different. The kinetic energy of the molecules increases so the rate of reaction also increases. That’s why shielding gas is used to protect the metal from reacting with unwanted elements of the air. However, a specific temperature has to be maintained for good quality TIG welding.
If you apply too much heat, the metal will be overheated beyond the ideal temperature. This will nullify the effects of the shielding gas. The metal shall remain molten due to overheating even after the removal of the shielding gas. This will cause unbearable discoloration and make the weld gray. It will also result in the degradation of corrosion resistance property of the weld.
When overheated, the molecular structure of the metal also changes. So, the color might change by default and cause a matte appearance.
3. Contamination
The electrode used in all-electric arc welding is consumable. It decays away as the work progresses and becomes a part of the bond itself. The electrode kind of works as a filler. The melting point of the electrode is the same as the heat applied to the welding base.
In TIG welding, the tungsten rod is used as an electrode. The rod is termed non-consumable because it does not decay. The base metal works as the filler. Although, a separate filler is used sometimes. The operating temperature is lower than the melting point of tungsten which is why the rod remains intact throughout the entire process.
Due to faulty technique, the tungsten rod gets overheated. Small bits of the electrode are blown off of the tip and go into the weld bead. This causes pores and also contaminates the weld. Due to contamination the weld becomes discolored and loses its lustrousness.
4. Wrong Shielding Gas
Shielding gas is used to protect the weld from oxidation. When the metal is molten and still too hot, it is prone to oxidation. Shielding gases are inert gases that shield the molten metal from the air. As they are inert, they do not react with the metal either. In TIG welding, usually argon is used as shielding gas.
You can mix helium with argon for better weld quality. This gives the welding more penetration and makes the weld pool more fluid. You can also add hydrogen or nitrogen to achieve similar properties. Adding hydrogen gives similar properties as helium, only stronger. Adding nitrogen improves the grade of nitrogen alloy.
However, you should keep in mind that the addition of hydrogen gas should only be in the case of austenitic stainless steel. Using hydrogen with argon has adverse effects on martensitic, ferritic, and duplex steel. Similarly, using improper shielding gas can make the weld look dull and discolored. The weld may lose shininess subsequently.
5. Excess Amperage
There is a specific amperage that needs to be maintained for proper TIG welding. The general rule is that the requirement of amperage is thousands of times per inch thickness of the material. If the parts you are welding are 0.01 inches thick, the required amperage is 10 amp. However, this example only applies as long as the material is 0.125 inches thick.
As the thickness increases from 0.125 inches, the required amperage also starts to decline. For example, you can weld a 0.375 inches thick part with about 300 amperes. Know that the specified amperage has to be strictly maintained. More amperage means more heat. This will bring about the effects of overheating.
Due to excess amperage, the weld can become discolored. It can turn grayish and lose its glossy appearance. The amperage is also dependent on the type of joint. T joints require more amperage than butt joints even if they are the same thickness. So always maintain proper amperage according to the thickness and the joint type.
6. Dirty Materials
The working area should be neat and clean. Even the tiniest bit of dirt is enough to ruin your welding. Clean the base metal properly before starting. Clean with cotton or soft cloth. Clean the tungsten electrode before starting to weld. If you plan to use filler metal, clean that too. Make sure the area you are in is also clean.
To clean everything properly, you can use a stainless-steel brush. It’s better to avoid any type of solvents like brake cleaner, hydrocarbon-based solvents, etc. If any dirt remains during the welding, it will become discolored subsequently.
7. Not Using Pulsed Welding
Pulsed welding is a highly precise welding technique. It can be applied to all forms of arc welding. It produces an attractive weld and exceptional finish. As TIG welding requires subtle hand-eye coordination, using the pulsed welding technique can be highly beneficial to achieve nice-looking shiny welding.
In arc welding, there is a steady flow of electricity to maintain the welding arc and keep the metals heated. In the pulsed welding technique, the amperage is never steady. Instead, it continuously fluctuates between low to high current. You control the amperage by the foot pedal, but the pulsed current is delivered from the TIG torch.
Not using pulsed welding can result in losing shininess. If your welding machine supports pulsed welding, go for it.
8. Wrong Polarity
Polarity can be a confusing issue in TIG welding. When welding any other metal than aluminum, DC is always used. The electrode is usually negative and the base metal is positive. This is termed DCEN which means ‘Direct Current Electrode Negative.’ It is also called ‘Straight Polarity’. In this process, the base metal gets the most heat.
But when welding aluminum, using AC is a must. In AC, the polarity is switched back and forth between the electrode and the base metal. For this, the electrode gets the most heat, unlike the DC. AC is used for aluminum welding because aluminum is highly reactive and forms aluminum oxide.
When the electrode is positive, the formed oxide is blown away. When the electrode becomes negative, it melts down the base metal. Thus, the welding progresses. If you use DC when welding aluminum, the aluminum oxide will form and the resulting weld will become dull and discolored.
9. Wrong Type of Tungsten Rod
There are several types of tungsten rods for different types of TIG welding. Thoriated 2%, ceriated 2%, zirconiated 1%, etc. are to name some. What many people don’t know is that each of these types is meant for a specific type of TIG welding.
Green-colored pure tungsten rods are used for AC welding of aluminum and magnesium. They are relatively inexpensive. 2% thoriated rods are 2% thorium mixed with tungsten. The mix of thorium makes the tungsten more durable. These tungsten rods produce cleaner weld because the rods leave no residue.
Gold-colored lanthanated electrodes can be used for both AC and DC welding. Lanthanated electrodes are more durable than thoriated. Many welders prefer lanthanated tungsten rods because thorium is radioactive. So, using a proper rod is essential for proper welding and a great finish.
If you use the wrong electrodes, your welding might end up disastrous. If you want shiny-looking welding, make sure to choose the correct rod. Consult an expert beforehand if needed.
Some Useful Tips for Successful TIG welding
TIG welding is all about precision. It doesn’t need any post-welding cleaning or finishing. So, the entire welding procedure has to be pitch-perfect. Here some tips for successful TIG welding:
- Maintain Proper Angle
The angle between the workpiece and the electrode is crucial. The ideal angle that needs to be maintained is 15 degrees. A slight variation won’t hamper much. Proper angulation means that you will have good access to the filler material and the filler will be easy to apply into the welding.
This will also give great visibility to the welding area. If the angle you are holding is more than 45 degrees, you will lose coverage from the shielding gas. The measurement of the angle also depends on what type of joint you are working on. For butt weld, 90 degrees is ideal. For fillet weld, the ideal is usually 45 degrees.
- Don’t Apply the Filler Directly
As the electrode here is non-consumable, sometimes a filler material is used. In stick welding, the electrode is decayed and turns into filler material but that is not the case here. The tungsten rod does not decay here. It is because of the melting point of tungsten being higher than the temperature applied for welding.
There’s a specific technique of applying filler in TIG welding. When welding, the electrode melts the base metal and forms a puddle. The filler is inserted into the puddle and melted by the molten metal. If you directly put the filler material with the electrode, this will result in a weak joint.
- Keep the Working Area Clean
Cleanliness is very important for a good outcome. Make sure everything in your working space is clean. The slightest dirt can have a big impact on the outcome of the welding. Especially for stainless steel and aluminum, a clean area must be maintained as they are highly reactive. Do not use any random object to clean the metals.
I recommend using a stainless-steel brush for cleaning the metals. Clean gently and make sure the air of the room is clean. Do not use brake cleaner or any similar solvents.
- Control the Amperage
Overheating can cause a lot of issues. Losing luster and color is the chief one. The correct amperage should be delivered when welding. If there’s more current, more heat will be produced. The shielding gas won’t have much effect and oxidation shall take place.
So, always use minimum power. Constant supply of power is more important than using excessive power. Using the optimum amperage will get you a solid, strong, and shiny weld.
How to Detect A Faulty TIG Weld?
It’s very important to be able to tell the difference between perfect and faulty TIG weld. Now, your TIG weld not being shiny is just one of the many indications of a poor weld. There are actually plenty of other indications like that. So, let’s take a look at some of the other manifestations of a faulty TIG weld:
- Porosity
Porosity is caused by oxidation. When the weld pool is exposed to air due to the presence of pockets in the shielding gas, small pores occur. The gas pockets can be a result of dirt presence on the base material. Also, exposure to breeze or gust can cause gas pockets which may result in porosity.
It’s easy to identify porosity. You will see small perforation on the final weld. Those are the ones you are looking for. Excessive gas pressure is also a reason behind porosity. Always maintain optimum gas pressure for a perfect weld. Keep the arc length as short as possible.
- Burnout
Overheat is the main reason behind burnout. Too much heat buildup results in excessive melting at the end of the weld. You can easily tell if your weld has burnt out. Look for decays or degradation at the point where your weld has ended. Burnouts look extremely bad and will ruin your TIG welding’s aesthetics.
Burnout can be mended by welding from both sides of the burnout and finally overlapping it.
- Undercut
A shallow groove on the weld surface along the bead is known as an undercut. The undercut is one of the main concerns of TIG welding because it heavily disrupts the aesthetics. Plus, there are multiple reasons behind the occurrence of the undercut. So, identifying the cause can be difficult.
Excess arc length, too much travel speed, wrong angulation, etc. can be the reason behind undercutting. Find out which one you are doing wrong and make amends accordingly. Try reducing travel speed and arc length first. If that doesn’t work, try other solutions.
- Inconsistent Finish
The size or the diameter of the filler material is important because of melting times. If the filler rod is too small, it will quickly melt and will brim over causing an inconsistent weld finish. Using too big of a filler material shall delay its melting. So, the material won’t flow into the correct spot, and desired adhesion won’t be achieved.
To get a smooth and lustrous finish, use filler material of appropriate size. Also, make sure the filler metal is the same as the base metal.
Conclusion
TIG welding is often used to make meticulously designed sculptures. This very information gives you an idea of how much clean and precise finish TIG welding can produce. It is all about practice, coordination, and mastery of the technique. Due to a lack of critical knowledge, you might not get the desired result from your TIG welding.
Here in this article, I have discussed 9 reasons your TIG welds aren’t shiny. If you’ve read the whole article, you will be able to select what your fault was and rectify it accordingly. I also added some tips about TIG welds and tried to explain why TIG welding is better. Hope this article offers you everything you needed to know about TIG welding. Thanks for reading and until next time, farewell.
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