1.What are the core influencing factors of food contamination resistance?
The core of food contamination lies in chemical attack by food ingredients on the coating, or in the coating's corrosion and release of substances that contaminate food. Therefore, the food contamination resistance of pre-coated coils depends primarily on:
The coating's chemical stability: whether it withstands attack by chemicals such as acids, alkalis, oils, and solvents;
The coating's density: whether micropores exist to prevent contaminants from penetrating the substrate and causing the coating to peel;
The coating's safety: whether it contains harmful substances such as heavy metals and volatile organic compounds, and whether these substances are released upon contact with food.
2.How does fluorocarbon coating resist food contamination?
Chemical stability: Fluorocarbon resin contains C-F bonds in its molecular structure, and its bond energy is extremely high (485kJ/mol). It is highly resistant to acids (such as organic acids in vinegar and juice), alkalis (such as baking soda), oils (such as vegetable oils and animal fats), and salts (such as sodium chloride in soy sauce and pickles). When exposed to these substances at room temperature, the coating will not dissolve, change color or peel off, nor will it release substances due to chemical reactions.
Limitations: If food contaminants contain strong solvents (such as alcohol concentration > 90%, acetone), long-term immersion may cause the coating to swell slightly (but not dissolve); contact with oils at high temperatures (> 150°C) may accelerate coating aging (but this temperature is rarely seen in food scenarios).
3.How well do polyester coatings resist food contamination?
Chemical stability: Polyester resin has moderate acid resistance, but is sensitive to strong alkalis and strong solvents. Long-term contact may cause the coating to lose gloss, change color, or even partially dissolve.
Resistance to grease and salt: Contact with grease (such as the oil film condensed by kitchen fumes) or salt (such as salt water for pickled food) at room temperature will not cause obvious damage in the short term (1-2 weeks), but in the long term (several months), the coating adhesion may decrease due to grease penetration, resulting in "bubbling" or partial peeling.
4.How well do epoxy coatings resist food contamination?
Chemical stability: Epoxy coatings are more resistant to alkali (better than polyester) and have good barrier properties to oils and fats (dense molecular structure), but are less resistant to acid (especially concentrated acid, such as vinegar, which may cause the coating to turn white and soften after long-term immersion).
Limitations: Epoxy coatings are relatively brittle. If local corrosion of the coating occurs due to contamination, the coating may break and fall off; and some epoxy coatings contain free phenols, which pose a safety risk if in long-term contact with food (not in compliance with food contact material standards).
5.What are the precautions in practical application?
Avoid direct contact with "edible food":
Additives may be used in the production process of the coating of color-coated coils. Although they meet industrial safety standards, they have not passed the food contact material certification and cannot guarantee safety when in contact with food. Therefore, they cannot be used for food packaging, tableware, or surfaces that directly contact ready-to-eat food.
Suitable for indirect contact scenarios:
If used for walls and equipment shells in food processing workshops, fluorocarbon or highly weather-resistant polyester coatings are suitable choices. Performance can be maintained through regular cleaning, and it is not easy for the coating to be damaged by pollution.
Influence of cleaning and maintenance:
Even for coatings with strong pollution resistance, if food contaminants accumulate for a long time, microorganisms may grow and decompose oils to produce acidic substances, which will indirectly erode the coating. Therefore, regular wiping with warm water + neutral detergent can extend pollution resistance.