For a strong weld, you need to clean the metal beforehand so there are no contaminants. This is because it can interfere with the welding, create resistance and even create a weld splash. So if the metal you want to weld has rust, paint, and dirt or mill scale then you need to clean it. There are many ways to safely clean your metal. Don’t worry if you don’t know what is best for you yet. In this blog, we are helping you decide by showing you how to clean your metal before a weld.
Before you weld, you should clean the surface with acetone to clear away contaminants. Even if you’ve removed all the rust and paint you’ll still need to wipe down the metal. There might be lingering particles that may react during the welding, and you risk doing all that removing for nothing.
Sandpaper is great for removing rust and paint. While courser grit will be faster it will also create scratches on the metal. An aluminium oxide paper will last longer on metal. If you are cleaning rust from machinery, 80 – 100 grit will do the job. If you want a nice finish for something like furniture, then don’t go any coarser than 150 grit.
Also known as sandblasting, abrasive blasting is mainly used for more advanced cleans. If the metal has a coating or is extremely rusty, then sandpapering it will probably be a waste of time. You’ll also need to blast the metal if the paint is bonded to the metal. This equipment is a pretty industrial, however, there are portable versions available.
If you need to get into odd angles and grooves then nothing will do the job like a wire brush. They are perfect for removing light contaminants like flaky paint, rust and weld splatter. You can use a crimped wire brush for fast and light cleaning or a knotted brush for things a little more heavy duty. However, a wire brush won’t be any good for removing anything bonded to the metal. You will need to take additional steps.
An angle grinder is fast and is best for removing big contaminants. You can use a flap disc or a sanding disc to remove rust, paint, mill scale and more. It will take a lot off, so if you are better off using an angle grinder on thicker materials. If you’re not careful you can gauge and ruin the metal you want to weld. Keep that in mind when you decide what the best method to clean your metal is.
Acid-like chemicals can be used to strip rust, paint and other contaminants away. There is always a risk using chemicals, if you are careful and know how to handle them then it shouldn’t be a problem. If not handled with care the fumes and the corrosive acid can cause some serious damage. Non-toxic chemicals can also be used but there will take a little more time to work.
If you are welding aluminium then you need to use a special method, as the metal is incredibly susceptible to contaminants. The first thing you need to do is wipe the metal with acetone. Then use a wire brush or acid to remove surface contaminants. Then rise and clean with acetone again. If you use the wire brush first then you won’t be removing the contaminants effectively. Instead, you will just spread them around and push them into stretches. If you are not immediately welding the aluminium then you need to cover it and keep it dry.
Things to avoid
There are pretty easy mistakes to make when cleaning metal. Before you start, read through this list:
- Make sure there are no deep grooves or marks. Contaminants can be buried deep within and are harder to clean out. It will also affect the quality of the weld and give you limited control.
- Cutting too much of the surface off, especially if the metal is thin, will ruin the strength and shape of the metal.
- If you don’t wipe down the metal there could be dirt, dust and oils that will ruin your weld and can lead to defects.
- Never weld when the metal is wet. After you’ve cleaned the metal make sure it is dry before you start welding.
- If you are using chemicals then you should handle them with extreme care. Make sure that they are covered and that you protect your skin and eyes when you use them.
Looking to invest in an affordable welder? Acra has a range of top-notch used welders to get you started. If you want to know more, please don’t hesitate to get in touch with us by calling 03 9794 6675.