LASER CLEANING TO REMOVE CONTAMINANTS FROM METAL SURFACES

Laser cleaning is an effective method to remove coatings in specific areas and contaminants on metals such as steel, aluminum and copper. This green manufacturing technology delivers a clean surface without damaging the metal substrate.

Laser cleaning achieves different processing speeds depending on the material being processed, the coating’s thickness and the cleanliness level that is required. Choosing between a single-mode and a multi-mode laser can also affect the results.

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How to Validate Laser Cleaning Quality

Laserax uses a range of standard, proven tests to ensure that the cleaned surface is free of any coatings or organic contaminants. First, the metal’s wettability is measured with a water contact angle (WCA) test.

Water Contact Angle

By measuring the contact angle on the cleaned surface with a surface analysis device, we can see if any contaminants prevent water from spreading. A lower contact angle (around 10 degrees) indicates a clean metal surface.

Reflective Fluorescence Units

Cleanliness is also measured with Relative Fluorescence Units (RFU). RFU values are registered by a fluorescence measurement device which irradiates UV rays on the metal surface and quantify the resulting fluorescence from the contaminants.

Just as we measure noise to quantifies silence, we measure the fluorescence of contaminants to measure cleanliness. The lower the RFU value, the cleaner the metal.

Single-Mode vs. Multi-Mode Lasers

Single-mode lasers convey laser light more efficiently and have a better beam quality in comparison to wider, more powerful multi-mode lasers. Both laser types can be used to remove contaminants for metal surfaces.

The main differences are that single-mode lasers can etch a surface texture during cleaning to improve adhesion whereas multi-mode lasers can clean surfaces faster.

CLEANING SPEEDS FOR COATING REMOVAL

Laser cleaning removes coating layers from metal surfaces without damaging the substrate. Laserax achieved the speed results below in multiple projects . Requirements included achieving WCA values of <= 10° and RFU values of <= 10. Coating removal was tested for different thickness levels on coatings such as:

Powder coating
Phosphate coating
E-coating (KTL, Cataphoresis)

Material	Description	100W	200W	300W	500W	1kW	2kW	3kW
		SINGLE-MODE [in²/s]				MULTI-MODE [in²/s]
E-coating & Phosphate coating	25μm	0.1 - 0.2	0.2 - 0.3	0.3 - 0.4	0.5 - 0.6	0.6 - 1.2	1.1 - 2.4	2.4 - 3.5
E-coating & Phosphate coating	50μm	0.08 - 0.1	0.1 - 0.2	0.1 - 0.2	0.2 - 0.3	0.3 - 0.6	0.5 - 1.2	1.2 - 1.7
Paint & Powder coating	100μm	0.03 - 0.1	0.1 - 0.2	0.2 - 0.3	0.3 - 0.4	0.5 - 1.2	1.9 - 3.6	3.9 - 5.1
Paint & Powder coating	200μm	0.01 - 0.05	0.05 - 0.07	0.08 - 0.1	0.1 - 0.2	0.4 - 0.6	1.3 - 1.7	2.0 - 2.6
Epoxy	0.5mm	0.02	0.03	0.06	0.09	0.12	0.17	0.19

CLEANING SPEEDS FOR OTHER MATERIALS & CONTAMINANTS

Laser cleaning is an effective method for cleaning metal surfaces of contaminants that have accumulated during production. Laserax achieved the results below in multiple projects with different requirements.

Material	Requirements	100W	200W	300W	500W	1kW	2kW	3kW
		SINGLE-MODE [in²/s]				MULTI-MODE [in²/s]
Oil	Esthetic Finish	0.9 - 1.4	1.6 - 2.2	2.0 - 2.6	2.6 - 3.0	18.6 - 32.7	39.4 - 63.2	62.3 - 91.1
	WCA = 30‑40	0.6 - 0.7	1.0 - 1.3	1.3 - 1.8	1.7 - 2.5	7.0 - 10.8	17.5 - 32.0	30.4 - 43.4
	WCA = 10‑20	0.4 - 0.6	0.7 - 0.9	0.9 - 1.3	1.3 - 1.6	1.2 - 3.3	5.4 - 10.2	9.8 - 17.0
Oxide	Esthetic Finish	0.8 - 1.0	1.8 - 2.0	2.5 - 2.9	3.6 - 5.5	18.6 - 32.7	39.4 - 63.2	62.3 - 91.1
	WCA = 30‑40	0.5 - 0.7	0.7 - 1.1	1.1 - 1.5	1.7 - 2.3	5.3 - 8.5	15.5 - 23.3	21.7 - 32.6
	WCA = 10‑20	0.3 - 0.5	0.6 - 0.9	0.9 - 1.3	1.3 - 1.6	1.7 - 3.9	5.3 - 9.6	10.0 - 14.5
Rust	Grade C	0.1 - 0.6	0.3 - 1.6	0.5 - 1.9	0.8 - 2.3
Mill Scale	General	0.01 - 0.09	0.03 - 0.2	0.05 - 0.3	0.08 - 0.5