Collision Repair Training | Australia
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Collision Repair Training | Australia
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Current Events/News: Advantage Online: 2003 Archives
REPAIR CONSIDERATIONS FOR EXHAUST PARTS March 10, 2003 -In the past, automotive exhaust systems were only expected to last a few years at best. Then in the mid-1970s, U.S. Federal environmental mandates for catalytic converters with five-year or 50,000-mile warranties forced vehicle makers to switch from mild steel to stainless steel as the material of choice for these parts. The advent of extended length warranties and increased consumer expectations has led to the factory exhaust of today’s vehicles typically having all of its parts made from some alloy of stainless steel.Stainless steels have high chromium content compared to other steels. By far the most widely used stainless steel alloy for factory exhaust parts is 409 ferritic stainless steel, which has the lowest chromium percentage of any stainless steel at 11.2% and a carbon content of only 0.010%. This makes it an economical choice for exhaust parts, while offering improved corrosion resistance over mild steel. For longer-term durability requirements, some exhaust parts may be aluminized or coated by hot dipping in a molten aluminum solution.
There are challenges to welding exhaust system parts in a repair facility. One challenge is obtaining the proper consumables to set up a GMA (MIG) welder to weld stainless steel exhaust parts. Using ER70S-6 steel electrode wire to weld stainless steel exhaust parts may lead to a corrosion problem at the weld zone. At least one OEM service manual recommends any welding done to the exhaust system be done with AISI 409 electrode wire. Many welding equipment suppliers do not stock 409 series electrode wire, as its main application is in the manufacturing sector. The electrode wire is also typically only available in large spool sizes of 16 kg (35 lb) or more. Solid 409 electrode wire is typically not found in diameters less than .035" and tubular metal-cored electrode wire diameters start at .045", meaning a liner change will be required before using it. The tubular electrode wires are also not designed for welding in the overhead position - a disadvantage when welding exhaust parts on the vehicle. The argon-oxygen shielding gas mixture is also typically not available in the smaller bottle sizes. This reduces the practicality of having the correct consumables on hand for the occasional job that requires exhaust welding.
There are also some additional health concerns when welding stainless steel. The nickel in stainless steel can cause asthma and cancer. The chromium can cause cancer, sinus problems, and “holes” between the nostrils. A welding respirator is required when welding stainless steel.
Additional information on exhaust system service is contained in the new I-CAR Enhanced Delivery course “Fuel And Exhaust Program 1.” Watch for it this spring in your area.
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