Last Updated on May 2022
Powder coating is famous for its adhesion and durability. However, the same qualities that make it so desirable pose considerable challenges in the event that you need to remove the coating.
Let us first evaluate the main reasons why you may need to remove powder coating:
- Renovation – to keep an old product looking all new and shiny
- Correcting errors – especially for newbies who are prone to making mistakes during the powder coating process
- Cleaning – for every powder coat applied, you need to clean off the racks and hangers to avoid unnecessary build-up as you complete the works.
Factors to Consider When Choosing a Powder Removal Method
- Desired surface finish
- Environmental and health regulations
- Project budget
- Material type and dimensions of the parts
- Speed of stripping
There are four primary methods used to remove powder coating:
- Chemical stripping
- Mechanical stripping/Media blasting
- Thermal stripping
- Laser Removal
1. Chemical Stripping
Chemical stripping methods use hot or cold stripping chemicals, which work by causing the powder coating to dissolve, soften and swell. The layer then independently falls off or sometimes needs to be washed off. This method removes powder coating entirely and evenly. However, handle cold chemical strippers cautiously as they are dangerous solvent-based products.
The various chemical strippers available are designed for different applications with consideration of the volume of production and frequency of powder removal. You may need to brush off any residual powder coating that may remain on the surface. Ensure you have a proper respirator at hand as well as a disposal plan for the chemical.
The safety of the user and the environment is critical when using this method.
Advantages
Removes all the powder coating from a surface, leaving you with a clean and even surface after the process is complete.
Chemical strippers work well with both occasional small productions as well as large productions. Chemical strippers and the accompanying equipment needed are affordable.
Disadvantages
Chemical strippers contain toxic chemicals that can be dangerous and hazardous to work with as they can easily burn the user’s eyes and skin. Users must wear proper personal protective equipment (PPE) like face masks all times.
Chemical strippers do not leave an anchor profile of the surface being stripped. An anchor profile is defined as the microscopic texture of the surface, which usually provides the new coating something to stick on. This is critical as it ensures the durability of the new coating applied.
The stripper and water used are often considered hazardous waste; therefore must be disposed of according to the required health and safety standards. This translates to a highly regulated and costly disposal process.
Chemical strippers involve an extra step in the process because you will need to leave behind a perfectly smooth surface, so you may need to scrape off the surface because it usually is too smooth.
Generally, chemical strippers are accompanied by a lot of strict environmental, safety, and health requirements.
2. Mechanical Stripping/Media Blasting
There are two types of mechanical cleaning systems: automated or batch operations. Mechanical paint stripper utilizes blasting media such as sand, water, carbon dioxide pellets, glass bead, steel shot, plastic media, slag, oxides, garnet. These are propelled under high pressure and speed in the direction of the coated material, therefore eliminating the coating through abrasion.
Dustless Blasting does not require a blast cabinet or containment, whereas dry Blasting can either be done in a blast cabinet or a blast room.
Abrasive media should be selected correctly as it affects the speed of removing the coating and the surface profile. Hard abrasive particles work faster in removing the coating quickly but leave the metal surface very uneven and rough. On the other hand, gentle blasting media, like soda or plastic, ensure a smooth metal surface but require more extended periods to clean.
If you intend to remove powder coating by sandblasting, it is advisable to use an aggressive blast media like steel grit or aluminum oxide. Aggressive media like these help to reduce the time taken to remove the powder coating. Also, it is important to note that compressed air is essential in production in sandblasting; therefore, ensure to invest in a large air compressor before starting the work process. For more information on the top rated air compressors [Read our Full Guide]
Tips and tricks for effective sandblasting:
Wet vs. dry Blasting for powder coating
Traditional sandblasting is not popular because it is quite a slow process for removing powder coating. The dustless blasting option is preferred because it is much faster than dry Blasting. This is due to the water it produces, which raises the output of the machine’s mass and energy, significantly increasing the speed.
Wet Abrasive Blasting
Wet abrasive Blasting is just like traditional sandblasting, only that the blast media is moistened before impacting the surface. This process is beneficial because it reduces dust, allowing users to work in diverse conditions with little set-up and clean-up costs. Its result is always a cleaner and even surface.
Portability Advantage
The use of water to suppress dust makes the use of Dustless Blasting an environmentally friendly process. It is also advantageous because it does not require bulky containment; therefore, it can be easily transported for use at your customers’ premises or any other convenient location.
Superior Paint or Coating Reapplication
It is possible to achieve various anchor profiles using different abrasives. This is an attractive quality because the right anchor profile is the foundation of excellent coating reapplication.
Danger of Rust
Please make use of the available rust inhibitor by rinsing the blasted metal in it, giving you rust prevention for 72 hours.
Advantages
It is useful for small parts as well as large batch work
It is portable therefore very convenient
It leaves an anchor profile that ensures proper reapplication and saves time that would otherwise be spent on scuffing the surface.
Disadvantages
It is slow compared to the heat and chemical techniques making it unsuitable for high production levels of powder coating removal.
It is costly and can get costlier if a blast room is required.
It requires compressed air, which can be limiting to specific work conditions.
3. Thermal cleaning
The thermal cleaning process may also be known as “burn-off,” “bake-off “or” fluidized bed.”
Thermal cleaning burns off the coating by exposing it to very high temperatures. After treatment, chemicals and ash residue are usually rinsed off with water or removed by blasting. For effective results, ensure that the parts are strong enough or resistant to temperatures as high as 650°C.
This method is preferable because it eliminates the hazards, risks, and headaches encountered when dealing with the chemical stripping process of coating removal.
The various options available to remove powder coating using heat include a bake-off, burn-off, or fluidized bed system. The difference in operation is demonstrated by the amount of heat utilized, different temperatures, and the speed of removing the powder coating.
- Bake off system – temperatures of 640 – 750 degrees Fahrenheit, take 3 – 6 hours to be cleaned. Wash off the burnt off powder coating so that it does not stick to the surface. Oven parts are equipped with water-misting systems that help to optimize the burning rate, which reduces damages.
- Burn off system – temperatures of 1000 – 1200 degrees Fahrenheit. They are usually installed as inline processes. Faster as it only takes minutes to be cleaned. Suitable for high production facilities due to its cleansing capabilities and extreme temperatures. When the burning process is complete, the fire is quenched water is used to remove any residual ash.
- Fluidized bed stripping system – temperatures of 800 degrees Fahrenheit. Parts are heated to disintegrate the coating, and the abrasive property of the medium eliminates all residues. Uses inert media such as sand and oxides as a heat transfer medium. The medium is fluidized under the influence of heat and gas or air pressure. No additional cleaning is required after the treatment.
Advantages
It is void of the strict environmental regulations found in chemical stripping.
Removing powder coating using heat provides one of the fastest ways to complete the process, even for a larger production. This makes it a very popular choice for operators.
In addition to speed, thermal cleaning is efficient with minimal environmental, safety, and health hazards and disposal issues.
Disadvantages
High power consumption – Equipment needed is costly, and power to maintain such a high temperature is even more expensive. For this reason, the location where such an amount of power is available is significantly minimized.
High chances of warping or damaging parts – This is due to the extremely high temperatures required to remove powder coating. Also, this technique does not leave an anchor profile needed for coating reapplication.
Longer processes – this method requires an additional cleaning or wash stage after powder coating removal in order to eliminate any burnt or powder remnants before proceeding to the next step.
4. Laser Removal
It is exciting to most operators to note that lasers have been specifically designed to remove coatings from a product surface. Due to its costly nature, it is imperative to ensure that proper background prepping is done and that it would work on the thickness of the powder coating you intend to remove.
Here’s a video showing how the process works:
Advantages
Works for both small and large surfaces.
Safe with no environmental restrictions.
Minimal alterations to the surface because no heating is involved.
Disadvantages
It is a very costly endeavor, and this limits its usage.
Laser removal does not profile the surface, after which it can set the user back a few steps.
Conclusion
With the options described above, you can compare notes and choose the best option depending on the volume of work, frequency of powder removal, and cost implications. However, the general rule of thumb is that:
- Sandblasting is cost-effective and has shorter preparation steps.
- Chemical stripper is best suited for occasional powder coating removal.
- Batch burn-off ovens are best suited for high production cases. It is the most expensive method yet among the fastest and most efficient alternatives available.
