By Alex Fraser on December 08, 2020
Laser Cleaning
The phosphating process, which makes use of phosphoric acid, is hazardous, with steps like degreasing, phosphate baths, water rinsing after phosphating, chromic acid rinsing, and wastewater treatment.
If you’ve ever stripped the phosphate coating off a part, or managed a phosphate conversion coating process, chances are you’ve seen your fair share of chemicals. Traditional phosphate removal methods rely on chemical strippers like hydrochloric and sulfuric acid. Other strongly alkaline and chelated solutions are just as dangerous.
If you want to get rid of chemicals during phosphate coating removal, laser cleaning may be the solution you’re looking for. This up-and-coming surface treatment is finding its place in many production lines that are looking to simplify their manufacturing process and diminish costs.
What Is Laser Phosphate Removal?
Laser phosphate removal, also known as laser coating removal, is the process of removing coatings using the heat of a laser beam. As the coating is heated, it is vaporized into dust and fumes that must be extracted with a proper fume extractor.
The laser beam can also be configured to strip coatings from localized areas with extreme precision. One of the most revolutionary applications is the replacement of part masking: the coating is simply removed from an area after coating the entire part. Surface preparation before welding is another important application.
The process leaves the metal substrate unharmed. The high temperature of the beam is enough to ablate the coating, but not the metal. Laser ablation can be used to clean metal parts of any type, including stainless steel. If you want more information on this reaction, read our article on how laser cleaning works.
Industrial laser cleaning can remove all types of phosphate coatings, including iron phosphate coatings, manganese phosphate coatings, and zinc phosphate coatings. It does not need to be followed with a secondary process since it also removes any contaminants that may be mixed with the protective coating, including oils and oxides.
The following video shows phosphate coating removal on pinions and ring gears.
The Advantages and Disadvantages of Laser Phosphate Coating Removal
Laser cleaning is a game changer for anyone who needs to remove phosphate coatings, but it’s not ideal in all situations.
The Advantages
- Cleaning is a fast one-step process (see examples of phosphate coating removal speeds).
- Parts are not damaged by the laser if it is set accurately.
- Maintenance and operative costs are extremely low.
- Waste is minimal and fully managed by a dust extraction system.
- Coatings can be removed from predefined areas in a highly selective way, which no other cleaning methods can do. This is a major innovation for manufacturers who need to clean certain areas only.
- Phosphate removal is easy to integrate in production lines using a laser cleaning machine.
- Workers don’t need to wear PPE, except if using a handheld solution.
- It’s an excellent pretreatment because the resulting metal surface has good coating adhesion and corrosion resistance.
- High-power fiber lasers equipped with a 3D autofocus system can easily strip coatings from curved and complex surfaces.
- It can be used with ferrous and non-ferrous metals alike.
The Disadvantages
- The laser requires a direct line of sight. This means that it may not be able to reach certain areas, such as with high aspect ratio cylindrical parts that are coated on the inside.
- Fiber lasers require a higher initial investment.
- Dust and fumes generated by laser cleaning are toxic and need to be extracted at the source with a laser fume extractor.
- The laser must be enclosed in a Class-1 laser safety enclosure to make sure workers are 100% safe. Alternately, access to the cleaning area must be restricted, and operators must wear PPE.
How Fast Is Phosphate Coating Removal?
The laser cleaning speed varies according to two main factors: the thickness of the phosphate crystals and the laser power. Other factors such as the type of metal and the type of coating have minimal impact.
Here are examples of cleaning speeds for iron-manganese coating on a steel part at room temperature.
| Laser Power | Phosphate removal speed |
|---|---|
| 100W | 1.5—2.3 cm2/s |
| 200W | 2.7—4.1 cm2/s |
| 300W | 4.6—6.9 cm2/s |
| 500W | 7.0—10.6 cm2/s |
Things You No Longer Need to Do When You Get Rid of Chemicals
Getting rid of chemicals can radically change your manufacturing process—in a good way. With laser cleaning, you no longer have to:
- Buy expensive chemicals and manage them
- Regularly remove the sludge that forms in tanks
- Oversee wastewater treatments
- Compute the coating weight to figure out the exact soaking time
- Struggle to meet environmental regulations
- Manage the dangers of workers being exposed to chemicals
If you think laser cleaning might be a better solution for you, contact one of our laser experts to discuss feasibility and obtain a free quote for your application.
