What measures are taken to prevent rust in car-bottom annealing furnaces?

Car-bottom annealing furnaces constitute large-scale industrial heating equipment employed for the thermal treatment of metallic materials, including processes such as annealing, normalising, and tempering. They find primary application across sectors including steel production, machinery manufacturing, metallurgy, automotive fabrication, and mould processing. Owing to their intricate construction and frequent operational demands, these furnaces typically function within environments characterised by high temperatures, dust accumulation, humidity, or the presence of corrosive gases. Consequently, both the main structure and critical components of industrial annealing furnaces are susceptible to corrosion damage. Severe corrosion not only shortens the equipment's service life but may also compromise heat treatment quality and operational safety.

Consequently, establishing systematic and scientific anti-corrosion measures is crucial for ensuring the long-term stable operation of car-bottom annealing furnaces. Manufacturers of industrial annealing furnaces will comprehensively address rust prevention strategies for cart-type annealing furnaces across multiple dimensions—structural design, material selection, surface treatment, sealing protection, operational environment, usage management, maintenance, and intelligent safeguards—aiming to cover the entire equipment lifecycle.

I. Enhancing Fundamental Rust Prevention Through Structural Design

Structural Optimisation to Eliminate Water Accumulation and Dead Zones

Design should minimise areas prone to water pooling and dust retention. Surfaces must remain smooth with no pronounced recesses or angles, particularly at furnace shell joints, door-to-body interfaces, and undercarriage rail bases. Incorporate appropriate drainage slopes or ventilation ports to prevent prolonged condensation and localised corrosion.

Enhanced Protective Cover Design

Rust-prone components (e.g., lifting mechanisms, rail guides, hydraulic cylinder casings, drive chains) should incorporate removable protective covers. These shield against moisture, dust, and corrosive agents while facilitating maintenance access.

Optimise Exhaust Ventilation Systems

Effective ventilation reduces humidity within the furnace and its surroundings. Designs should integrate natural and forced ventilation to prevent moisture accumulation on furnace surfaces, thereby avoiding the formation of corrosive microclimates internally.

II. Material Selection as a Corrosion Defence Line

Select corrosion-resistant metals for critical components

For elements such as furnace shells, trolley wheels, bearing housings, and steel structural supports, employ oxidation-resistant materials including stainless steel, chromium alloy steel, and hot-dip galvanised steel. This is particularly vital for areas enduring prolonged exposure to furnace gases, high humidity, or condensation.

Substitute rust-resistant materials for auxiliary components

For instance, replace standard carbon steel screws with galvanised equivalents, and substitute conventional steel casings with aluminium alloy cladding. Though non-load-bearing, these details represent common corrosion hotspots.

III. Surface Treatment Processes: The Critical Step in Rust Prevention

Sandblasting or Shot Blasting for Rust Removal

Prior to coating application, all steel components must undergo mechanical rust removal to eliminate scale, rust spots, oil residues, and other contaminants. This ensures coating adhesion and fundamentally enhances rust prevention efficacy.

Multi-layer coating protection system

For high-corrosion areas such as the car-bottom annealing furnace shell, rails, and car wheel hubs, employ a three-layer or multi-layer coating system: primer (zinc-rich paint), intermediate coat (epoxy-based), and topcoat (polyurethane or acrylic). This provides excellent barrier properties alongside UV resistance and chemical durability.

High-Temperature Zones Require Heat-Resistant Anti-Corrosion Coatings

For high-temperature zones such as furnace doors, openings, and combustion chambers, specialised heat-resistant coatings (e.g., silico-aluminate heat-resistant paint) must be selected to prevent loss of protective efficacy due to carbonisation of standard coatings at elevated temperatures.

Localised galvanisation or thermal metal spraying

Components subject to mechanical friction or frequent exposure, such as guide rails, limit pins, and lifting hooks, may be treated with hot-dip galvanisation or arc-sprayed zinc-aluminium alloys to form durable barriers.

IV. Sealing Protection Measures to Isolate Corrosive Media

Waterproof Sealing Design

All interfaces, gaps, and openings should incorporate flexible sealing pads, silicone gaskets, or high-temperature resistant sealants to prevent external moisture ingress into the furnace interior. This is particularly crucial during rainy seasons or in humid regions.

Furnace Door Sealing System Inspection and Replacement

The high-temperature resistant sealing strip between the furnace door and body must maintain elasticity and integrity. Regularly inspect for ageing or cracking to prevent condensation forming during cooling after heat treatment. This prevents temperature differentials between the furnace interior and exterior from causing condensation, which could lead to corrosion of the furnace door.

V. Optimising Operating Conditions to Reduce Corrosion Triggers

Controlling Workshop Humidity and Ventilation

The equipment operating environment must remain dry and well-ventilated. Particularly during northern autumn and winter seasons and southern rainy seasons, dehumidification systems or forced ventilation measures should be implemented to minimise moisture-induced corrosion of the furnace body.

Controlling Furnace Gas Contaminant Accumulation

If exhaust gases from the bogie-hearth annealing furnace are not effectively vented, they may condense into acidic substances that corrode the furnace shell and internal components. Therefore, the exhaust system must remain unobstructed, with regular removal of accumulated dust or slag deposits within the furnace.

Prevent Condensation from Thermal Shock

Optimise furnace cooling cycles to avoid rapid temperature drops or significant environmental temperature differentials that cause moisture to condense on metal surfaces.

VI. Strengthening Anti-Corrosion Measures in Operational Management

Standardise Operating Procedures

Prevent mechanical damage, coating deterioration, and moisture ingress caused by non-standard operations (e.g., forceful door operation, overload running, or wet start-up).

Prevent Incorrect Use of Water Washing or Wet Cloth Wiping

Many operators use water to clean furnace surfaces for convenience, which severely damages the anti-corrosion coating. Water washing is strictly prohibited, especially on the bottom of the car and slideway areas. Cleaning should be performed using dry cloths, dust extractors, or oil-based cleaning agents.

Prompt drying procedures

In the event of leaks, steam condensation, or splashed water, immediately wipe dry and employ hot-air drying to prevent localised rust formation.

VII. Regular maintenance to extend service life

Routine inspections and coating repairs

Conduct monthly inspections of furnace shells, trolley base plates, tracks, and other critical areas. Should coating peeling, corrosion spots, or rust patches be detected, promptly grind away rust and reapply paint.

Addition of Rust Inhibitors and Lubricants

Periodically inject high-temperature grease containing rust-inhibiting components into moving parts such as bearings, axles, and chains to provide both lubrication and corrosion protection.

Lubrication and Drying Management

Regularly remove accumulated dust from furnace door lifting mechanisms, locking devices, and similar components. Apply dry film lubricants or graphite coatings to prevent accelerated corrosion caused by dust absorbing moisture.

Establish Equipment Anti-Corrosion Logs

Document all maintenance, inspections, and anti-corrosion coating applications to facilitate long-term tracking and predictive maintenance scheduling.

VIII. Introduction of Intelligent Anti-Corrosion Technologies

With the advancement of Industry 4.0, increasingly sophisticated intelligent management and protective measures are being integrated into heat treatment equipment:

Temperature and Humidity Monitoring Systems

Continuously monitor ambient conditions around the furnace. Trigger alarms or activate ventilation systems when humidity exceeds threshold levels to prevent corrosion-prone environments.

Surface Corrosion Monitoring Sensors

Corrosion rate sensors or intelligent coating delamination detection systems installed at critical points provide early warnings of rust progression, enabling proactive maintenance.

Intelligent Spraying Robots

Robots are increasingly deployed for precision coating in the manufacturing or maintenance of large car-bottom annealing furnaces. This enhances coating consistency, uniformity, and adhesion, improving rust prevention effectiveness at source.

Conclusion

As vital heat treatment equipment in industrial production, trolley annealing furnaces require comprehensive rust prevention throughout their entire lifecycle—encompassing design, manufacturing, installation, operation, and maintenance. Rust prevention extends far beyond mere paint application; it constitutes a highly integrated systems engineering endeavour involving material selection, structural design, construction techniques, environmental control, and intelligent operation and maintenance.

Only through scientific, systematic, and standardised rust prevention management can the safety risks and economic losses caused by corrosion be effectively mitigated, extending equipment service life while ensuring the stability of heat treatment processes and consistency in product quality. This constitutes not merely a fundamental requirement for equipment maintenance, but also the cornerstone of an enterprise's long-term operational sustainability.