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Dirty Welds: Consequences & Prevention

Dirty Weld

In the course of action through your career as a welder, you will frequently find yourself in situations that require you to weld metals that are in less than pristine condition, having sustained a fair amount of wear-and-tear through many years of use.

When you're called upon to make repairs out in the field, you're often presented with rusty, dirty, and greasy metals, not to mention metals that are completely covered with paint. Odds are you will find some combinations of these conditions (and sometimes all of them at the same time) on most of the jobs you're asked to perform. Even when making repairs in the shop, you’ll often be dealing with metals that are rusted, dirty and covered with paint, similar to what you might when making repairs in the field.

New metals also have their fair share of issues, given that many are covered with various coatings intended to preserve and protect the raw metal (galvanized steel being a prime example).

Preserving the integrity of your welds

Rust, dirt, grease, paint and many coating materials can compromise the integrity of your welds. These substances can contaminate the weld puddle, creating imperfection in the weld, compromising the welds overall strength. Additionally, paint and certain coating materials will be vaporized when super-heated by a welding. This vapor can be toxic and make you very sick if inhaled (the zinc coating in galvanized steel results in Fume Fever), and can also introduce air bubbles into the weld, severely compromising the overall strength of the weld. Long story short, it’s in your best interest for every welding project you work on to make sure the metal you’re working with is clean and clear of contaminates, and ready to rock!

The Cleaning process

The cleaning process depends to some degree on the type of metal you’re working with and the type of contaminant you’re trying to remove.

Let’s say you need to make some repairs to a semi-truck that’s seen quite a bit of road wear. The section you need to repair is definitely dirty, covered with some rust and grease, and to top it off, somewhere along the line the metal was painted to match the rest of the rig.

1.      Hit the whole area with a degreaser

2.      Use an angle grinder to remove the rust and paint

3.      Wipe down the weld area with acetone, using a clean shop rag

The degreaser eliminates the grease, the grinder removes the outer dirt, the rust and most of the paint, and the acetone will attack any linger elements that the first two clean methods may have missed.

Now you’re all clean and ready to weld!

*Please Note – Carburetor cleaner, and other similar automotive related cleaning chemicals are often used to clean metal before welding. You should, however, pay close attention to chemical interaction that may occur when these materials are super-heated by a welder. When vaporized, some chemicals are highly toxic and can cause stroke or death. Make sure you read all of the warning information included with these chemicals, and if you’re unsure, look it up online or just don't use it—always better off safe than sorry!

Dylan Brown


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