Best welding rod for rusty metal

Welding rusty metal can be a challenging task for even the most experienced welder. Rust creates an unstable surface that can cause the weld to crack, result in porosity or lack of fusion. To achieve a strong and good quality weld on rusty metal, it is essential to:

Choose the right welding rod, or
Clean the rust before welding.

Best Stick welding rod for rusty metal

Your best welding rod options to weld on rusty metal surface are:

E6010,
E6011, and

E7018.

E6010 and E6011 rods are commonly used for welding on rusty metal as they are having higher penetrating power and more silicon to contain rust and use on dirty or contaminated surfaces.

E7018 rod is also a good choice for welding on rusty metal. 7018 rods have higher manganese content that can control the adverse effects of the rust. Although, penetration is less with 7018 rod compared to 6010 or 6011.

6013 and 6012 rods are not recommended for use on rusty metal as they are not designed for use on dirty or contaminated surfaces.

Best TIG welding rod for rusty metal

ER70S-2 is a good choice when TIG welding rusty metal as it contains a high amount of deoxidizers that helps to remove impurities in the metal.

This helps to prevent porosity and other defects that can occur when welding on rusty metal. Additionally, it also has high strength and ductility which helps in welding rusty metal.

Cleaning the surface before welding is still recommended to remove as much rust as possible.

Best MIG welding rod for rusty metal

When MIG welding rusty metal, it’s best to use a wire that is specifically designed for welding on dirty or contaminated surfaces, such as the ER70S-2.

Effect of Rust on Welding quality

Rust can have a significant effect on the quality of a welding job. Rust can contaminate the surface of the metal, which can lead to porosity, lack of fusion, and other defects in the weld.

In addition, rust can also cause the metal to become weaker and more brittle, which can make it more difficult to achieve a strong weld.

Furthermore, the presence of rust can also affect the composition of the metal and its ability to form a stable arc during the welding process.

This can lead to difficulty in maintaining a consistent welding process, resulting in irregular welds and potential defects.

"Due to presence of oxides (rust is basically iron oxide), the weld metal will not be able to fuse with the base metal and consume most of deoxidizer presents in the wire. 

Resulting in insufficient deoxidizer and resulting in welding porosity. Also, Manganese being a deoxidizer is also responsible for strength and toughness- hence these two properties too will be decreased."

Therefore, it is important to properly clean the metal surface before welding to remove as much rust as possible.

This will help to ensure that the metal is in the best possible condition for welding and will result in a higher-quality weld.

Steps of welding on Rusty Surface

Read more: Does Galvanized Steel Rust?

To weld on a rusty metal surface successfully, follow these steps:

Clean the surface:

Make an assessment of the rusting condition. If its heavily corroded and there is significant thickness loss, better to replace the part.
For mild to moderate rusting, use a wire brush or grinder to remove as much rust as possible from the surface of the metal. This will help to ensure that the metal is in the best possible condition for welding.

Degrease the surface if available:

Use a degreaser or solvent to remove any oil or grease from the surface of the metal. This will help to ensure that the metal is clean and free of any contaminants.

Prepare the metal:

If the metal is thin or otherwise weak, it may need to be reinforced before welding (you can use fish plate for reinforcement). This could include adding a patch or backing plate, for example.

Set up the welding equipment:

Make sure that the welding equipment is set up properly and that the correct welding technique and rod (e.g., E6010 or E6011 or E7018 only) or wire (preferably ER70S-2) is being used.

Weld the metal:

Begin welding the metal using the stringer bead welding technique. Take care to maintain a consistent arc and to keep the metal clean and free of contaminants.
On heavily rusted surface, grind away the first layer and apply fresh weld layer. For sheet metal, use a smaller diameter rod such as 1/8 inch.

Inspect the weld:

After the welding is complete, inspect the weld to ensure that it is of high quality and that there are no defects present.

Clean the surface again:

After the welding is complete, use a wire brush or grinder to remove any slag or other debris from the surface of the metal.

Perform any necessary post-weld treatments:

Depending on the type of metal and the application, it may be necessary to perform post-weld treatments such as heat treatment or paint to protect the metal from rusting again.

It’s also important to note that some of the steps may vary depending on the specific welding technique and the type of metal being welded.

FAQS

Can you weld rusty metals?

Yes, it is possible to weld rusty metal, but it can be more challenging than welding clean metal. As mentioned previously, rust can contaminate the surface of the metal, which can lead to porosity, lack of fusion, and other defects in the weld.
In addition, rust can also cause the metal to become weaker and more brittle, which can make it more difficult to achieve a strong weld.