The Application of Laser Rust Removal in Rail Transit Maintenance

I. Introduction

Rail transit equipment—including metro systems, high-speed rail, light rail, trams, and locomotives—operates in complex environments. Metal components are frequently exposed to rain, humidity, dust, and salt-spray conditions, leading to corrosion and surface oxidation. Rust not only affects the appearance of rolling stock but also reduces material strength, increases friction losses, creates safety risks, and raises maintenance costs.

Traditional rust removal methods such as grinding, sandblasting, and chemical pickling rely on consumables, manual labor, or chemical agents, and often cause environmental pollution, safety risks, and insufficient precision. With the maturation of laser cleaning technology, laser rust removal has demonstrated significant advantages and is being increasingly adopted in rail transit maintenance.

II. Working Principle of Laser Rust Removal

Laser rust removal utilizes a high-energy-density laser beam irradiating the metal surface. The rust layer, oxide layer, or coating absorbs the laser energy, resulting in instant vaporization, thermal shock, or photochemical ablation, which removes the contamination layer from the substrate. In contrast, the metal substrate reflects most of the laser energy and is therefore minimally affected.

Common equipment types include:

Pulsed Laser Cleaning Systems — precise thermal control, suitable for high-value or precision components

Continuous-Wave (CW) Laser Cleaning Systems — higher throughput, suitable for large-area treatments

III. Typical Application Scenarios in Railway Transit Maintenance

Laser rust removal is applied in the following maintenance scenarios:

1. Rolling Stock Exterior Surface Treatment

Steel car bodies and outer shells exposed to environmental conditions tend to corrode over time. Laser cleaning is used prior to repainting or refurbishing, providing:

Substrate integrity protection

Improved coating adhesion

Zero abrasive dust contamination

2. Bogie and Undercarriage Components

Critical components such as bogies, frames, brake beams, and axle box covers are sensitive to surface damage. Mechanical grinding may introduce micro-scratches, while laser cleaning is suitable for:

Localized rust removal

Oil and coating removal

Surface pretreatment for inspection

3. Rail and Fastener Maintenance

Rails and fastening systems suffer corrosion in tunnels, coastal lines, and humid environments. Laser cleaning can be applied to:

Rail clips and bolts

Contact surfaces

Pre-welding surface preparation

4. Weld Seam & Electrical Contact Treatment

Corrosion impacts weld quality and electrical conductivity at critical interfaces such as:

Rail welding joints

Traction contact interfaces

Electrical terminals and connectors

Laser cleaning is suitable for oxide removal prior to welding, coating, or conductivity inspection.

IV. Advantages Over Traditional Processes

Compared with sandblasting, mechanical grinding, and chemical pickling, laser rust removal offers the following advantages:

(1) No Substrate Damage

Laser cleaning relies on selective absorption, maintaining surface geometry, making it suitable for precision components.

(2) No Consumables & Zero Chemical Pollution

Operation requires only electrical power, aligning with environmental and emission-reduction standards in the railway industry.

(3) High Automation Compatibility

Laser systems can be integrated with:

Industrial robots

Automated inspection lines

Maintenance management systems (MES)

to improve consistency and throughput.

(4) Applicable to Complex and Localized Structures

Suitable for treating:

Deep cavities

Grooves

Non-planar surfaces

which are difficult for chemical or mechanical cleaning.

(5) Reduced Rework Costs

Clean, uniform surfaces enhance coating performance and corrosion protection, extending maintenance intervals and reducing lifecycle costs.

V. Challenges and Development Trends

Despite its advantages, several challenges remain:

1. Higher Initial Investment

Laser systems cost more than grinders or blasting systems, although long-term operating costs are lower.

2. Large-Area Efficiency Constraints

Whole-carbody rust removal requires:

High-power CW laser configurations

Robot-assisted path planning optimization

3. Operator Training Requirements

Laser equipment requires standardized safety and operational training.

Future development trends include:

High-power continuous cleaning solutions

Machine-vision-based surface recognition

Automated cleaning robots for depots

Adaptive beam control & surface identification

VI. Conclusion

Laser rust removal is a clean, efficient, and controllable surface treatment technology that is becoming an important tool in railway transit maintenance. It addresses environmental and safety concerns while enhancing precision, reducing labor, and extending maintenance intervals. With decreasing equipment costs and increasing automation, laser cleaning is expected to achieve broader deployment in the railway transit sector, with strong market potential and engineering value.