Haikou’s Government Procurement Case for China VI Dongfeng 3308 mm Wheelbase Sewage Treatment Vehicles: A Practical Analysis from Corrosion Resistance to High-Load Operation. Haikou, located at the northern edge of the tropical zone, features a tropical maritime monsoon climate characterized by year-round high temperatures and abundant rainfall, with an annual average relative humidity exceeding 80%. Coastal areas are severely affected by salt fog corrosion. The municipal sanitation department’s aging sewage treatment vehicles—having been in service for over eight years—suffered severe frame rusting and seal degradation, resulting in frequent leaks and significantly increased failure rates during rainy-season operations. This procurement involved three small-scale sewage treatment vehicles, primarily intended for emergency sewage suction and preliminary treatment in urban drainage networks and low-lying areas. The procuring entity specified the following requirements: (1) Chassis must comply with China VI emission standards to facilitate local registration and annual inspection; (2) The complete vehicle must exhibit strong corrosion resistance, particularly for the frame, tank body, and piping system, requiring robust anti-rust coatings; (3) Critical sealing components must withstand hot-humid conditions and remain functional for at least three years; (4) The vehicle must support high-frequency, continuous operation during the rainy season, with uninterrupted working time per shift of no less than six hours. II. Technical Selection and Solution Overview Based on the client’s requirements, Chengli recommended the CLW5070GSSD6 model sewage treatment vehicle, modified from the Dongfeng 3308 mm wheelbase chassis (referencing MIIT announcement parameters). With a 3308 mm wheelbase, this light-duty truck–class vehicle offers excellent maneuverability on narrow urban roads while maintaining adequate payload capacity. Key configuration highlights include: Chassis: Original Dongfeng China VI chassis with approximately 85 kW power output, meeting urban operational power demands. According to Chengli’s product database, this chassis is widely used across municipal sanitation applications—including water sprinklers and vacuum sewage trucks—with high parts interchangeability. Tank and Piping Corrosion Protection: A dual-layer coating system comprising epoxy zinc-rich primer and chlorinated rubber topcoat, supplemented by an additional anti-corrosion wax treatment. Salt fog testing follows GB/T 10125 standards, achieving over 720 hours without red rust formation. Sealing Component Selection: All seals—including those for pumps, valves, and tank openings—are made from wet-heat-resistant nitrile rubber (NBR) or fluororubber (FKM), rated for operating temperatures from –20°C to 120°C, and validated through 1,000-hour salt fog aging tests. Operational Capability: Equipped with a high-capacity sewage pump delivering up to ~120 m³/h maximum suction/discharge flow rate. Effective tank volume is approximately 3 m³ (referencing vacuum sewage truck specifications), suitable for short-distance transport. III. Real-World Performance of Anti-Rust Coatings and Humid-Heat Resistant Seals Following delivery to the Haikou Project, Chengli’s after-sales service team conducted a three-month follow-up field evaluation. Key findings include: 1.