Stainless steel containers are made of a steel alloy with chromium included the content. The chromium keeps the steel from rusting or staining easily, something that would be more likely to occur if the container was made of another grade of steel. Many types of food can react with the stainless steel container so avoid storing some types of food in them. For safety, buy stainless steel food storage containers that are completely stainless, not stainless-steel-plated. Containers that are stainless-steel-plated tend to get chips in the coating and once that occurs, they are no longer safe to use, as the flakes can get into your food.
Over time, storing tomato-based foods in stainless steel containers can cause the container to pit. When foods cause pitting, they create tiny holes or cavities in the steel that you may not be able to see. The problem with pitted containers is not that the metal will leach but that the pitting will make the containers harder to get completely clean. Common tomato-based foods are pasta sauces, pizza sauces, tomato juice, tomato soup and tomato salad.
If you are pickling foods such as eggs, vegetables, olives, herring and corned beef in a salt solution, don't use a stainless steel container. The salt solution that is used in the pickling process can cause the stainless steel to suffer from pitting corrosion. This occurs over time as the salt solution sits in the container. Once a container starts to pit, it is impossible to reverse the process.
Don't store acidic foods in stainless steel containers for the same reason as pickled foods: the food can pit the container, making it less possible to get it completely clean. The longer the food is in contact with the stainless steel, the greater the likelihood of the pitting. Common acidic foods include tomato-based foods, as well as eggs, yogurt, cooked meats, plums, prunes, gravy, organ meats and cheese.
While vinegar is often used to clean stainless steel appliances and other items made of the steel alloy, long-term exposure to food items containing vinegar can cause the material to pit. So, find other containers for vinaigrettes, salad dressings, baked beans, cucumber salad, and some types of coleslaw, barbecue sauce, hot sauce, and potato or macaroni salad.