Can coating spray refers to the thin protective layer applied inside metal food and beverage cans to prevent corrosion and keep the contents from reacting with the metal. In industrial settings, this coating is sprayed onto the interior surface using high-pressure airless nozzle systems while the can body rotates, then dried and cured with heat. The process is invisible to consumers but plays a critical role in food safety, shelf life, and flavor preservation.
What Internal Can Coatings Actually Do
Without an internal coating, the acidic or salty contents of a can would corrode the metal within weeks. Tomato sauce, citrus juice, fish, and carbonated drinks are especially aggressive. The spray coating creates a barrier between the food and the steel or aluminum, preventing metal ions from leaching into what you eat and stopping the food from eating through the can wall.
The most common coating materials fall into a few categories. Oleoresinous coatings are the least expensive option, made from naturally occurring oils with synthetic modifications. They produce a golden-colored lining and are applied at 4 to 10 grams per square meter. Epoxy lacquers use epoxy resins blended with phenolic resins or zinc oxide, applied more thinly at 3 to 5 grams per square meter, though they’re not ideal for highly acidic products. Polyester coatings have proven effective for products like fish curry, maintaining acceptable chemical, texture, and sensory qualities for up to six months at warm storage temperatures. Vinyl and phenolic lacquers round out the approved options in most regulatory frameworks.
The BPA Problem With Epoxy Linings
For decades, most internal can coatings were based on epoxy resins containing bisphenol A (BPA). The concern: when the polymerization process is incomplete, or when cans are heated, BPA migrates from the lining into the food. Canned foods contain two to four times more BPA than products in plastic or paper containers. Canned food specifically carries about 40 times the BPA concentration found in canned beverages.
Heat accelerates the problem significantly. BPA levels in cans heated to 100°C (boiling temperature) were 1.7 to 55.4 times higher than in unheated cans. This matters because canned goods are sterilized during manufacturing and often heated again by consumers.
BPA mimics estrogen in the body, even at low doses. It has been linked to metabolic disorders, obesity, cardiovascular disease, reproductive cancers, fertility problems, and developmental issues in children. The FDA set a tolerable daily intake of 50 micrograms per kilogram of body weight, while the European Food Safety Authority set a stricter limit of 4 micrograms per kilogram. The EU also capped BPA migration from packaging at 600 micrograms per kilogram of food.
BPA-Free Alternatives Now Dominate
The industry has shifted dramatically. Roughly 95 percent of food cans are now made without BPA-based linings, according to the can manufacturing trade group. The replacements include acrylic resins, polyester resins, oleoresins, and olefin polymers.
Not all alternatives have been equally welcomed. PVC-based resin emerged as a popular substitute, showing up in 19 to 25 percent of cans tested by consumer advocacy groups. PVC raises its own environmental and health questions, so the transition away from BPA hasn’t been a clean win across the board. Still, the variety of available coating chemistries means manufacturers can match the lining to the specific food product, acidity level, and shelf life requirement.
How FDA Regulates Can Coatings
In the United States, internal can coatings fall under FDA rules for indirect food additives, specifically 21 CFR Part 174 and related sections. The core principle is that any substance migrating from a food-contact article into food must not exceed the amount reasonably required to achieve the coating’s intended function. The coating material must also be of suitable purity for its intended use.
For substances that migrate at negligible levels, the FDA offers a threshold-of-regulation exemption, meaning a full food additive petition isn’t required. This streamlined pathway has helped newer BPA-free coatings reach the market faster, though each formulation still needs to demonstrate safety before commercial use.
Effects on Recycling
Internal polymer coatings complicate aluminum recycling. Unlike anodized finishes, which don’t interfere with remelting, organic coatings like lacquers and spray linings must be thermally removed before the metal can be recycled. This de-coating step burns off the polymer, releasing CO₂ and contributing to dross (waste residue) during melting. The process still works, and coated cans remain recyclable, but the extra thermal step adds energy cost and emissions compared to recycling uncoated or anodized aluminum.
Consumer Spray Paint for Metal Cans
If you searched “can coating spray” looking for spray paint to use on metal cans for crafts or upcycling projects, the principles are simpler. Oil-based spray paints designed for metal surfaces, like Rust-Oleum’s professional line, bond directly to aluminum and steel without requiring a separate primer. They work on both interior and exterior surfaces.
For the best adhesion, clean the can surface thoroughly to remove any residue or oils. Lightly sanding with fine-grit sandpaper helps the paint grip smooth aluminum. Apply thin, even coats and allow full drying between layers. These consumer products are not food-safe and should never be used on surfaces that will contact food or beverages.