Coatings are typically added to metal surfaces to grant additional protection against corrosion, or to provide an aesthetic surface finish. Sometimes however, they need to be removed to improve adhesion, or to make sure there are no contaminants on areas to be welded. Existing coatings may also need to be removed as part of a refurbishing operation.
Whether you’re looking to remove phosphate coating, e-coating, powder coating, or epoxy, there is no single method that works for all applications. Laser cleaning, chemical stripping, abrasive blasting, burn-off ovens, induction heating, and other surface preparation methods all come with different benefits and limitations.
In this article, we will go over five common coating removal methods and when you should use them. Finally, we will look at three real use cases
Coating Removal Methods Considerations
There are several factors to consider when choosing a method. Important considerations include:
- The type of coating
- The coating thickness
- The part geometry
- The surface area that needs to be cleaned
- The volume of parts to be processed
- The part positioning method
- Your budget
1. Laser Cleaning
Laser cleaning, also known as laser coating removal and laser paint removal, sweeps the surface with a laser beam to remove coatings. The laser beam generates just enough heat to vaporize the coating without damaging the metal substrate. You can find more information on how laser cleaning works here.
Laser cleaning is the best solution to quickly clean localized areas, as it offers a level of precision unmatched by other methods. However, it is not ideal for large surfaces because the coating removal process will take too long.
Laser cleaning requires a higher initial investment than traditional methods, but it provides a better return on investment in high-volume productions. It is also easy to automate and helps manufacturers meet their green goals, since there are no consumables or chemicals involved.
2. Chemical Stripping
Chemical stripping uses a chemical solution to dissolve, soften, or swell coatings. The paint stripping chemical that is used depends on the coating that needs to be removed. Each type of paint stripper is specialized at removing a specific type of coating.
The process provides some of the best cleaning results, but it comes with downsides. Here are the most important ones:
- When using chemical stripping, the chemical solution’s temperature needs to be controlled to achieve the best effect. Typically, it needs to be maintained at high temperature, which drives up operative costs.
- In industrial environments, chemical baths are often used to immerse parts in chemical solutions. Several rinsing steps are needed during the process, which generates wastewater that needs to be treated and disposed of properly.
- Chemicals can be dangerous for workers’ health and safety. Appropriate measures need to be taken such as PPE to chemicals management.
3. Abrasive Blasting
Abrasive blasting is a generic term for methods that propel blasting media at high speed onto a surface. Examples of abrasive blasting methods include sandblasting, grit blasting, dry ice blasting, and shotblasting.
Abrasive blasting methods can strip coatings faster than other methods and require a lower initial investment, but they come with several downsides:
- Generate a considerable amount of waste
- Must be performed in a controlled environment with personal protective equipment
- Cannot be used for coating removal operations requiring precision
- Aggressive types of media may damage the substrate
- The residual blasting media needs to be removed to prevent surface contamination
4. Burn-Off Ovens
Burn-off ovens use very high temperatures (up to 1,000°F) to burn combustible materials, turning them to ash. There is no fire involved during the process because the oven is deprived of oxygen. Once the coating is all burned off, remaining ashes are removed through various means, such as water rinsing.
Even if the cleaning results are good, high temperatures can cause damage the substrate in various ways (stress, brittleness, metal fatigue). Finally, burn-off ovens use a lot of energy to reach and operate at high temperatures, driving operative costs through the roof.
5. Induction Heating
Induction heating is a method that generates heat in a metal substrate to break the bond between the coating and the metal. The coating can then be completely removed without the need for external agents such as a blast medium. In the preceding video, an induction coating removal system is used to clean a steel substrate.
Coating Removal Applications & Examples
Laserax provides laser cleaning solutions for manufacturers who use lasers to remove several types of coatings, including phosphate coatings, e-coatings, and powder coatings. Let’s look at some examples.
Phosphate Coating Removal Before Assembly
Our fiber lasers are used to remove phosphate coating from pinions and ring gears to prepare them for assembly. More specifically, the phosphate layer causes reliability problems in specific areas and has to be removed from those areas only.
Related blog post: Phosphate coating removal without chemicals
E-coating Removal to Replace Masking
In driveshaft production lines, masking is used to cover certain areas before e-coating. The process is time consuming. Manual errors can also force operators to remove the entire coating and start over the coating process.
Laser cleaning replaces masking to speed up the coating process and prevent manual errors. Instead of masking the areas that need to be free of coating, driveshafts are completely coated, then the e-coating is removed from specific areas using laser cleaning.
Here is an example of laser cleaning machine used to replace masking for e-coated parts:
Related blog post: What are the best methods for e-coating removal?
Powder Coating Removal
Laser cleaning is used to remove powder coating from specific areas, such as the aluminum plate in the previous video. It is used in electric stator production lines to get rid of masking. Instead, the entire electric stator is coated, then the coating is removed from the assembly areas only.
We hope this article helped you choose a method for the removal of coatings. If you’re interested in laser coating removal, our experts can help you implement the process in your production line, providing everything you need to make sure the operation is a success. This includes additional features such as a laser fume extractor to make sure the dust and fumes generated by hazardous coatings are managed properly.