10 Tips For Welding A Catalytic Converter

Catalytic converters can make a big impact in your welding shop. By following these tips, you can increase the efficiency and quality of your welds.

Types of Catalytic Converters

There are three main types of catalytic converters: solid state, metal-organic, and ceramic (MOC). Solid state catalytics work without any material being present between the two electrodes. Metal-organic catalytics use an alloy of metals to create a catalyst that helps the weldment take place. Ceramic catalytics use ceramic particles or flakes to help with the welding process.

Solid state catalytics work best when used in combination with a metal-organic or ceramic electrode; they can also be used standalone if you have a suitable metal source available. Metal-organic catalysts are most effective when used in conjunction with other metals, such as aluminum, chrome, cobalt, copper, gold, iron, nickel, platinum, silver, and tungsten; however, they can also be used standalone if desired. Ceramic catalysts are more effective when used alone but can also be combined with other materials for better results.

Metal-organic catalysts use aluminum as their primary electrode; however, there are many other possible aluminum sources that may be used including bronze (copper/chromium), carbon (aluminum/carbon), chromium (aluminum/chromium), copper (aluminum/copper), gold (aluminum/gold), gunmetal (aluminum/gunmetal), hf steel (aluminum/hf steel), lead (aluminum/lead), molybdenum (aluminum/molybdenum) and tin (aluminum/tin).

Ceramic catalysts typically require no extra material other than some ceramic particles or flakes to help with the welding process; however, they may sometimes require additional support like a pot or rod set up next to the catalyst bed so it can contact both materials evenly during welding.

When it comes to welding cats:

1) Follow these general tips when welding cats:

a) Use caution when working around sharp edges or hazards;

b) Always clean your area before starting welds; and

c) Make sure both materials are completely dry before starting the welds.

Step by step instructions for welding a catalytic converter:

1. Clean off the surface rust and any other foreign material that has accumulated on the surface.

2. Make sure that you are using a TIG welder, not a stick welder, as it will give you better results at reducing the amount of heat that your welds need to stay together while they cool down.

3. Make sure that you have your electrodes and clamping devices lined up correctly before starting to weld. If necessary, have your part lay on an angle grinder with its flat side under the machine’s work table to get it positioned correctly.

4. Start on the inside of your catalytic converter and tig weld it in place. This will help prevent the possibility of cracking and thinning of your part because you have less area to work with on the outside radius of the converter. You may, however, want to use multiple passes when welding a seam to limit excess heating and cooling cycles, but make sure that you do not make each pass thicker than the previous one. Using too much heat when welding can cause cracks and thinning of your part.

5. While you are welding, try to keep your torch angle about 60 degrees for an inside-out joint and about 45 for a side-to-side joint. You may want to increase the angle depending on where you are working in relation to the exhaust pipe, as more room is necessary when welding from the inside out. Do not forget to wear your protective clothing and shielding materials.

6. Try to keep your weld seams less than three inches apart and keep the total thickness of your welds at around a quarter of an inch or less. If you have to use multiple passes, try not to make them thicker than the previous one each time around.

7. Make sure that your deposit gun hose screen is clean after each pass and before starting the next one.

8. After you have finished welding the inside of your catalytic converter, weld the outside of it, making sure to go back and fill in any gaps that you may have missed between the two weld seams with another tacking pass. Again, remember to avoid overheating your materials while you are working on it by keeping everything on a level plane and try not to let anything get in front of your outlet electrode while it is live or in between passes.

9. Last, clean up your welds with a grinder before you paint the converter.

10. After cleaning off any excess paint, you are ready to reinstall your catalytic converter. Remember to plug in your O2 sensor wherever applicable before putting it back into place and sealing it with silicone or some other kind of non-reactive sealant.

11. Start your car, and check the converter to make sure that everything is working the way that it should be.

10 Tips for Welding a Catalytic Converter

  • Use as few clamps as possible.
  • Weld from the inside out for a side-to-side joint.
  • Make your seams about three inches apart and your welds about a quarter of an inch thick.
  • Use multiple passes, but don’t make each one thicker than the previous one if you have to.
  • Clean off any surface rust before tacking in your place your welds, especially if you are using a TIG welder, as this will help keep them from cooling unevenly or not at all.
  • When tacking in your welds, try to keep the side of your electrode that you will be welding against perpendicular with the surface of your material. This will help avoid having to grind out a lot of excess weld when you get to that part later on.
  • Keep your torch angle about 60 degrees for an inside-out joint and about 45 for a side-to-side joint. You may want to increase the angle if you are using a TIG welder, which works better when it has more room to move around in between the arc and the metal being worked on, or if you are working in a smaller place with less room to move around.
  • If you are using an angle grinder to grind out excess weld, use a coarse grinding wheel.
  • Make sure that you clean your deposit gun screen after each weld and before starting the next one.
  • Use your exhaust safely when welding on or near any exhaust pipes.


Welders should use the right tools to weld catalytic converters, minimize welding time, and weld catalytic converters the way they were meant to be welded. With proper techniques and using the correct tools, you can create high-quality products that will help your business reach a larger audience.


Edward, a seasoned welding expert, shares his extensive knowledge and insights on Welderit.com to help you enhance your welding skills.

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