For the corrosion protection of emulsion cranes (cranes used in emulsion environments), it is necessary to combine the chemical characteristics of the emulsion (oil, water, surfactants) with the working environment (high humidity, frequent splashing), and adopt a five dimensional comprehensive strategy of structural protection, coating protection, environmental control, lubrication maintenance, and electrochemical protection. The specific methods are as follows:

1、 Structural protection design: reduce corrosion risk from the source

Material selection optimization

Prioritize the use of steel with stronger corrosion resistance (such as Q345B+N galvanized layer, 316L stainless steel), and avoid direct exposure of ordinary carbon steel (Q235) in the emulsion splash zone.

Perform surface galvanizing treatment (hot-dip galvanizing layer thickness ≥ 80 μ m) on key structural components (such as main beams and support legs) to form a physical isolation layer.

Structural sealing design

The welding area adopts continuous welds to avoid crevice corrosion caused by spot welding or intermittent welding.

Seal the enclosed chambers of the frame, arm frame, etc. (such as applying sealant, installing waterproof cover plates) to prevent emulsion from seeping into the interior and forming corrosive batteries.

Optimization of drainage system

Design drainage holes (diameter ≥ 10mm) at the bottom of the frame and support legs to prevent corrosion of the bottom caused by emulsion water accumulation.

Tilt the installation of structural components (such as boom) to ensure that the emulsion can quickly flow away after splashing, reducing dwell time.

2、 Coating protection system: Building multi-layer protective barriers

Primer selection

Use epoxy zinc rich primer (dry film thickness ≥ 80 μ m) with zinc powder content ≥ 80%, and protect the substrate through sacrificial anode action.

Pre coat zinc rich coating and polish smooth areas such as welds and corners that are prone to corrosion to avoid cracking caused by excessive coating thickness.

Intermediate paint and topcoat

The intermediate paint adopts epoxy mica iron intermediate paint (dry film thickness ≥ 120 μ m) to enhance the adhesion and impermeability of the coating.

Polyurethane topcoat (dry film thickness ≥ 60 μ m) is selected as the topcoat, with excellent chemical resistance (emulsion resistance, salt spray resistance) and weather resistance, and a gloss retention rate of ≥ 80% (5 years).

Coating construction control

The surface treatment reaches Sa2.5 level (sandblasting rust removal), with a roughness of 30-70 μ m, ensuring coating adhesion of ≥ 5MPa (pull-out test).

When coating in layers, the interval between each layer should be controlled within 4-24 hours (at an ambient temperature of 25 ℃) to avoid a decrease in interlayer adhesion.

3、 Environmental control: reduce the concentration of corrosive media

Emulsion management

Control the pH value of the emulsion between 6-8 to avoid metal corrosion caused by strong acidity or alkalinity.

Regularly replace the emulsion (every 3 months or based on concentration testing results) to prevent the growth of microorganisms and the production of corrosive metabolites.

Isolation of homework area

Install water barriers (height ≥ 1.5m) between the emulsion processing area and the crane operation area to reduce splashing.

Install rain covers (IP65 rating) on sensitive parts such as the crane cab and control cabinet to prevent direct contact of emulsion.

humidity control

Install dehumidifiers in the crane storage area to maintain an ambient humidity of ≤ 60% (RH) and suppress electrochemical corrosion reactions.

Strengthen ventilation during the rainy season to avoid the formation of condensation on the surface of structural components.

4、 Lubrication maintenance: block contact with corrosive media

Lubricating grease selection

Use NLGI grade 2 waterproof lubricating grease (such as lithium based composite grease) containing anti rust additives (such as molybdenum disulfide) to form a durable protective film.

Lubricate the pulley system, bearing seat, and other parts every 50 hours to ensure full coverage of the contact surface.

Lubrication point protection

Install a dust cover on the grease filling port to prevent emulsion from entering and causing grease emulsification failure.

Regularly clean the lubrication system (such as oil cups and oil pipes) to prevent impurities from blocking and causing local oil shortages.

Hydraulic oil management

Choose anti emulsification hydraulic oil (such as ISO VG46 anti-wear hydraulic oil) containing demulsifier components to reduce the delamination time of the oil after mixing with water.

Replace the hydraulic oil every 2000 hours and replace the filter element synchronously (accuracy ≤ 10 μ m) to prevent accelerated corrosion of metal particles.

5、 Electrochemical protection: supplementary measures for localized corrosion

anodic sacrifice protection

Install zinc blocks (purity ≥ 99.99%) on easily corroded parts such as the frame and legs, and prioritize the corrosion of the zinc blocks through electrochemical action to protect the substrate.

The consumption of zinc blocks is calculated at 5% per year and is replaced regularly (usually every 2 years).

External current cathodic protection

For large structural components such as main beams, titanium based mixed oxide anodes are used, and a protective potential of -0.85V (relative to the Cu/CuSO4 reference electrode) is applied through a DC power supply.

Install a reference electrode (high-purity zinc) to monitor the protective effect and ensure a stable potential between -0.85V and -1.05V.

6、 Regular testing and maintenance: dynamically adjust protection strategies

Coating inspection

Measure the coating thickness with a film thickness gauge every six months, and repair any local damage (diameter ≥ 5mm) immediately.

Inspect the coating pinholes with an electric spark detector (voltage 5000V), and mark the repair area (expanding to 20mm around the defect) after discovering the defect.

Structural Inspection

Every year, ultrasonic thickness gauges are used to measure the wall thickness of the main beam and support legs. If the thinning amount exceeds 10%, the remaining service life needs to be evaluated.

Perform magnetic particle testing (MT) on welds, with a focus on identifying transverse welds in the emulsion splash zone.

Corrosion rate monitoring

Install corrosion test pieces (A3 steel) on the frame, legs, and other parts, and weigh and calculate the corrosion rate quarterly (≤ 0.03mm/year is qualified).

Adjust protective strategies based on monitoring results, such as increasing coating thickness and shortening lubrication cycles.

7、 Emergency response plan: Quickly respond to corrosion issues

Temporary protection

After discovering the coating damage, immediately cover it with waterproof tape and complete the repair within 24 hours.

Polish the corroded area with sandpaper to St3 level (visible metallic luster) first, and then apply fast drying anti rust paint (such as zinc yellow primer).

structural reinforcement

If there are localized corrosion pits (depth ≥ 2mm) on the main beam, repair by welding with patch steel plates (thickness ≥ 6mm), and the welds must undergo 100% UT testing.

If the inclination of the support leg exceeds L/1000 (L is the length of the support leg), the foundation needs to be readjusted and reinforced.

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