While welders work hard to clean their metal work pieces, stack up their welds, and minimize spatter when laying beads, contaminated welds can sometimes happen. On occasions these contaminated welds will change colors. Sometimes a weld changes colors but isn’t necessarily contaminated. And sometimes welders contaminate their welds on purpose in order to create specific colors.
Colors are especially common in stainless steel welding when there are oxides in the metal. These oxides cause the various colors in a weld and prevent the steel from resisting corrosion. Over the long term corrosion is usually a problem for welds, however, there are different standards (available at the American Welding Society) from one industry to another when it comes to these colors in welds.
How to Prevent Oxidation in Welds
When the integrity of the weld is on the line, a good shielding gas set up, typically using Argon, is essential in order to prevent oxidation while welding. Cleaning the weld ahead of time can make a big difference too, but if some colors do show up, you can usually clean the metal when done. However, darker colors mean there is more oxidation and the integrity of the weld may be in question.
If you have the option of switching to pulse while welding, that can lessen the heat and give yourself a chance for deeper penetration into the metal. This will give you a stronger weld that won’t be as susceptible to oxidation and cracks.
Weld Colors and Welding Stainless Steel
Welding stainless steel is the most common process where corrosion and colored welds come into play. In many applications, such as medical or aerospace, there is no room for error, so any colors on the weld are not allowed under code.
However, in some farm applications, a light blue streak in the weld is acceptable under most codes or can be removed fairly easily. A darker color than light blue or a rainbow pattern is usually a sign that there has been significant oxidation in the weld joint.
Welding Art and Colorful Welds
A colorful weld joint isn’t always a bad thing, especially when you’re creating art. Some welders even go out of their way to include a little rust in their work pieces. They may seek out particular metals or types of rusty metal in order to enhance the colors in their workpieces. 308 stainless steel is a favorite of many artists when seeking to create vivid designs.
In some instances you can manipulate the amount of shielding gas in order to alter the colors of your weld. However, there certainly are exceptions to this as well.
Colorful Welds and Welding Titanium
Welding titanium can also yield some striking results when the metal is allowed to oxidize, with striking blues and purples becoming the favorites of welders who are willing to take a chance on this process. However, in the case of titanium, the metal is far more brittle than stainless steel, and that means there are more chances of the weld’s integrity being threatened by oxidation.
In the majority of cases, you don’t want any colors showing up when welding titanium, no matter how brilliant they can become. Welders working on automotive applications may still decide that it’s worth the risk.