Removing an e-coating protection may seem counterintuitive, but it’s an essential step in several manufacturing processes. It is often removed before welding to prevent weld contamination, to rework part rejects with irregular coatings, or to clean up equipment (hooks, racks, etc.) used for the coating process.
The most common methods for e-coating removal include burn-off ovens, sandblasting, and chemical stripping. A more modern technology is laser cleaning. It is adopted by manufacturers who need speed and precision, as well as those who want to get rid of consumables.
Keep reading to better understand what each technology is good at. But first, let’s review the coating process itself.
What is E-Coating and How Does It Work?
E-coating, or electro coating, is a painting process that uses an electric current to apply paint to metal surfaces. The e-coat improves corrosion protection and makes products last longer. In the automotive industry for example, it is used to protect critical safety parts like seat brackets, brakes, and driveshafts.
It is similar to powder coating, but each process has its distinct advantages.
With e-coating, parts (typically made of sheet metal) are immersed in a chemical solution that includes epoxy resin, paste, and deionized water. A precise voltage is sent into the solution to make the coating adhere.
E-coating is a highly precise process that achieves a uniform thickness with the same micron precision all over the surface.
How Do You Remove an E-Coat?
The four main methods for e-coating removal include laser cleaning, burn-off ovens, sandblasting, and chemical stripping.
Laser cleaning uses laser ablation to remove all types of contaminants from metal surfaces. By generating just enough heat, the e-coating is vaporized from the surface (along with other contaminants), and the bare metal is left intact. Paint particles are released into the air during the process, so an efficient fume extractor is needed.
Laser cleaning is ideal in situations where localized areas need to be cleaned, such as with welding. Unlike other methods, it can be integrated directly in the production line to process a large volume of parts.
Laser cleaning is typically much faster at removing e-coating than it is at removing powder coating because the coatings tend to be thinner. For industrial applications, laser systems should not be used to fully clean large parts, as the process will be too long.
As their name suggests, burn-off ovens literally burn off combustible materials. The coating is transformed into ashes. Since the oven is oxygen-deprived, no fire is involved in the process. These ovens are used in the finishing industry to clean up racks, hooks, fixtures, and parts. They can operate for several hours at extreme temperatures—going up to 1,000°F.
Although the cleaning quality is good, the high temperatures at which the substrate is subjected can cause stress, brittleness, and metal fatigue. This operation also requires additional steps, where residual ashes need to be cleaned off through water rinsing or other means. Also, running a burn-off oven uses a lot of energy and is thus a very expensive operation.
Sandblasting, or abrasive blasting, is perhaps the most widely known surface cleaning method. It is commonly used in the finishing industry to remove e-coat deposits from racks.
This operation must be performed in a dedicated room where operators wear PPE. Unlike other methods, sandblasting lacks precision. The more aggressive types of media can also cause loss of metal. After sandblasting, the residual blasting media need to be carefully removed to prevent dirt contamination. Operative costs also add up quickly, as consumables often need replacement.
Chemical Stripping Solutions
Chemical stripping is a process where entire parts are immersed in a chemical solution kept at a high temperature. Paint strippers are chosen for their ability to attack specific contaminants while leaving the bare metal intact.
Chemical stripping provides high-quality results, but it does involve a fair amount of chemicals on the shop floor as well as several rinsing steps and, hence, rinse water disposal. For these reasons, many manufacturers choose to outsource this process.
The process typically lasts between 30 minutes or a full hour, making it faster than burn-off ovens. It is also more precise than sandblasting, but it cannot be used to clean specific areas like laser cleaning.
How to Test Laser Cleaning for E-Coating Removal
If you have a project that requires e-coating removal, contact a Laserax expert today. Laser technology is probably a good fit for you if you need to remove e-coat from localized areas, process a large volume of parts, automate the cleaning process, or improve quality.