Can Sandblasting Garnet Cause Metal and Bodywork Warping?

Sandblasting metal, such as the thin body panels of a car, with garnet or other blast abrasives can cause some warping issues. Oftentimes we hear the question “is this caused by heat created from the abrasive or from peening of the abrasive impacting the sheet metal”?

People are often told that this is due to heat and still some people believe that it is from peening, and still others state that sheet metal warps due to peening, not from heat but from the compressed air. Whatever the way it is widely understood in the industry that sandblasting can warp sheet metal.

Sheet Metal Warping Because of Heat & Peening of Sandblast Abrasive

Sandblasting sheet metal may cause warping so this is something to carefully consider when choosing a blast abrasive such as garnet.

Experimenting with etched designs in plexiglass (plastic acrylic glass) it has also been noted that the surface can actually begin to melt when using certain types of abrasive. Although this doesn’t have the same heat resistance that steel sheet metal does, it still shows that sandblasting can cause a large amount of heat to build-up.

Abrasives also heat up sheet metal making it more malleable so that it peens easier. So even a little bit of heat can make warping more likely.

How to Prevent Sheet Metal from Warping While Blasting

If you are concerned with thin sheet metal warping while garnet sandblasting, here are a few recommendations for you:

  • Don’t Concentrate on one area for too long. The recommended technique is to move the abrasive spray back and forth across the panel instead of directing it at one area until that spot is fully clean. Otherwise this can cause heat to build up too much in that specific area.
  • Watch your blast angle. It is recommended to aim the abrasive spray at a 45 degree angle to reduce peening and heat build-up.
  • Lower air pressures. A lower air pressure can help reduce impact heat and peening on thin sheet metal.
  • Use fine abrasive grits. Most people use course abrasive such as 70 grit or larger. A finer grit of 150 or 180 may reduce peening. I am not sure if it would reduce or increase heat build-up.

Choose the right abrasive. Aggressive abrasives like coal slag or garnet can generate more peening and heat. The KinetiX and EpiX abrasives are a good choice for blast media that will efficiently and effectively help you deal with peening and metal warping.

Currently, KinetiX and EpiX are available from abrasive distributors around the US. If you don’t see a distributor near you, contact 10X and we will work with you to get you what you need. EpiX abrasive, which is best for precision applications such as powder coating and medical applications, is also available to purchase directly from the 10X Engineered Materials website.