In the early morning, the petroleum product pipe couplings, treated with a painting process, were neatly arranged in the production workshop. The surface paint film was smooth and uniform, having completed the processing steps for appearance and basic protective layers. At this time, workers were systematically applying rust-proof oil to each coupling. This step is a critical process that ensures the storage, transportation, and performance of the products—rust-proof oil forms a dense protective film on the surface of the couplings, effectively isolating air, moisture, and external impurities, preventing rust issues during storage, transportation, and before subsequent use. It directly impacts the stability of product quality and service life. The application process strictly adheres to standardized procedures, with workers carefully controlling the thickness and coverage of the rust-proof oil to ensure every surface is uniformly coated without omissions or buildup. Once the rust-proof oil has naturally penetrated and stabilized, the staff stack the couplings according to standardized packaging requirements, using a "one layer of cardboard, one layer of product" method. The cardboard effectively cushions impacts during transportation while preventing direct friction between products that could damage the paint film or protective layer, further safeguarding the appearance and protective effect of the products. After being stacked in layers according to standardized procedures, the products undergo final packaging and are promptly arranged for shipment, ensuring qualified products are accurately delivered to customers, laying a solid foundation for the smooth execution of subsequent petroleum-related operations.