As a mainstream metal lunch container widely used for student meal storage, outdoor camping dining, office worker portable meals, light food packaging and snack storage, the rectangular lunch tin container features high temperature resistance, plasticizer-free property, recyclability, deformation resistance and no peculiar smell compared with plastic and disposable lunch boxes. As a daily catering utensil in direct contact with hot and cold meals, fruits and vegetables, cooked food and oily food, its material safety, physical performance, temperature resistance stability and environmental compliance must be supported by systematic and standardized authoritative tests. Ordinary low-cost tin lunch boxes on the market generally have problems such as incomplete test items and perfunctory sampling inspection, which easily cause potential safety hazards including heavy metal precipitation, substandard high temperature resistance of coatings, peeling off due to acid and alkali corrosion, residual peculiar smell and pressure cracking. These problems will not only fail to ensure dietary health, but also lead to failure of supermarket entry, cross-border customs detention and frequent terminal customer complaints. Centering on the core production standards of full-item testing, whole-process testing and full verification, this rectangular lunch tin container establishes a closed-loop testing system covering raw material incoming inspection, production process patrol inspection, finished product full inspection, sampling inspection and compliance filing. All test items are in line with domestic catering utensil safety standards and European and American export specifications, serving as a high-safety standard portable metal lunch container for commercial, household and cross-border export use.

　　Special raw material testing locks the bottom line of food contact safety from the source. The substrate of this lunch tin container adopts brand-new original food-grade tinplate. After each batch of raw materials enters the factory, specialmetal material composition testing is conducted first to verify iron base purity, tin coating composition and heavy metal content, strictly control the limit of harmful heavy metals such as lead, cadmium, mercury and chromium, and eliminate the risk of excessive heavy metals caused by doped recycled iron materials. Meanwhile, coating adhesion testing and pinhole testing are carried out to detect missing plating, thin plating and pinhole defects of the tin coating, ensuring uniform and dense coating on the substrate surface and fundamentally avoiding metal exposure, food corrosion and metal precipitation. For the food-grade protective coating on the inner wall of the lunch box, special coating safety testing is implemented, including harmful substance migration testing, residual solvent testing, benzene-free and formaldehyde-free verification, preventing inferior coatings from precipitating harmful substances when contacting high-temperature meals, acidic fruits and oily food. All raw material test data are filed and archived to realize traceable materials, queryable data and accountable problems for each batch.

　　Full-item food contact migration testing adapts to all categories of meal storage scenarios. Since the lunch tin container is frequently used to hold high-temperature cooked food, acidic fruits, pickled food and high-oil meals, it strictly implements food simulant migration testing. Water, acetic acid solution, ethanol solution and n-hexane are used to simulate water-based, acidic, alcoholic and oily food respectively to carry out immersion migration tests at different temperatures and durations. The test focuses on verifying heavy metal migration, volatile organic compound migration and coating particle shedding, ensuring that no harmful substances precipitate or material components migrate to pollute meals during normal temperature storage, warm meal placement and short-term high-temperature heating. Meanwhile,acid and alkali corrosion resistance testing is completed. After long-term immersion testing, the inner wall of the box shows no discoloration, peeling, shedding or corrosion, thoroughly solving the common problem of blackening, corrosion and delamination of ordinary tin boxes when contacting acidic food. It fully complies with domestic GB 4806 food contact utensil safety standards and is suitable for safe storage of various daily meals.

　　Physical performance limit testing ensures long-term stable and durable use. A complete set of physical performance tests are carried out for the lunch tin container targeting daily opening and closing, stacking storage and transportation, outdoor collision and alternating high and low temperature use scenarios. Firstly, compression deformation testing is conducted to simulate stacking storage and logistics extrusion conditions, test the deformation degree of the box body under constant pressure, and ensure the tin box is flat and non-deformable with tight box mouth fitting, avoiding box depression and sealing failure caused by stacking extrusion. Secondly,opening and closing durability testing is performed to verify the fitting degree of the box cover and box body through tens of thousands of repeated opening and closing cycles, ensuring structural stability without loosening, deviation or jamming after long-term use. In addition, high and low temperature weather resistance testing is completed to simulate extreme environments such as refrigerator refrigeration, outdoor normal temperature, winter low temperature and summer high temperature, verifying material stability without embrittlement at low temperature, deformation at high temperature, coating cracking or peculiar smell release. Furthermore, burr safety testing is implemented for edge polishing parts to fully check the smoothness of box edges, cuts and opening positions, eliminating sharp burrs and edges to ensure safe use without scratches for students and adults.

　　Sealing and sanitary performance testing eliminates hidden dangers of pollution and moisture. The optional food-grade silica gel sealing strip independently completes food contact safety testing and aging testing to verify material stability after repeated stretching, bending and high and low temperature storage, ensuring the strip is free from hardening, cracking and harmful precipitation for long-term safe and compliant sealing. Meanwhile, the whole box undergoes air tightness testing through negative pressure air tightness test to verify the dust-proof, moisture-proof and soup leakage-proof capabilities, keeping internal meals clean and dry. Before delivery, finished products strictly implement sanitary cleanliness testing. Batch sampling is conducted to detect bacterial colonies, dust residue and peculiar smell residue after production in dust-free workshops, eliminating impurity, bacterial and odor residue during production. The finished products are clean, odorless and impurity-free, meeting the sanitary standards for direct use of catering utensils without secondary cleaning.

　　Environmental protection and printing compliance testing adapts to domestic and foreign market access requirements. All surface printing processes of the tin box are matched with ink environmental protection testing to verify VOC content, heavy metal residue and migration indicators of environmentally friendly soybean ink, ensuring printing areas are non-toxic, harmless, food-safe, scratch-resistant and fade-proof without dust shedding during long-term use. Meanwhile, degradable environmental protection testing and solid waste compliance testing are completed. The recyclable and reusable tin box produces no non-degradable harmful residues, complying with domestic plastic restriction policies and European and American environmental access standards. All auxiliary materials and processes pass compliance tests, avoiding market access risks such as excessive printing, substandard environmental protection and unqualified auxiliary materials, enabling smooth passing of domestic supermarket random inspections, e-commerce platform quality inspections and overseas customs compliance verification.

　　Final finished product comprehensive verification testing builds a closed-loop quality assurance system. Before delivery, all finished products undergo 100% visual inspection plus batch sampling full-item testing, covering five major testing sections: material safety, food migration, physical performance, sealing sanitation and environmental compliance. Each batch of products is provided with complete test reports, material qualification certificates and compliance qualification documents. A strict rework, scrapping and traceability rectification mechanism is implemented for unqualified products to prevent defective products from entering the market. Supported by the systematic full-dimensional testing system, this rectangular lunch tin container boasts four core advantages: safety, durability, sanitation and compliance. It adapts to full-scenario applications including household bento storage, student meal carrying, outdoor camping, enterprise customization and cross-border export. With stringent testing standards, it safeguards the safety of every catering use and serves as the preferred high-quality portable metal lunch box.