Let us take the mystery out of caring for stainless steel. Despite what you may have heard, stainless steel IS susceptible to rusting. In fact, corrosion on metal is common. It is easily recognizable on iron and steel as unsightly yellow/orange rust. Therefore, such metals are labeled active because they actively corrode in a natural environment. When their atoms combine with oxygen rust begins to form. Stainless steels are passive metals because they contain other metals, like chromium, nickel, and manganese, in order to stabilize the atoms
Kinds of Stainless Steel
- 400 series stainless steel are called ferritic, contain chromium, and are magnetic
- 300 series stainless steel are called austenitic and contain chromium and nickel
- 200 series stainless, also austenitic, contains manganese, nitrogen, and carbon
- Austenitic types of stainless are not magnetic, and generally provide greater resistance to corrosion than ferritic type
With 12-30 percent chromium content, an invisible passive film covers the steel surface, consequently acting as a shield against corrosion. As long as the film is intact and not broken or contaminated, the metal is passive and stainless. If the passive film of stainless steel has been broken, equipment will start to break down. As the corrosion continues, the steel will rust.
Enemies of Stainless Steel
Three basic things can break down the stainless steel passivity layer and allow corrosion to occur:
1. Mechanical abrasion. Mechanical abrasion refers to objects that will scratch a steel surface. For example, steel pads, wire brushes, and scrapers are all abrasive objects.
2. Deposits and water. Tap water has varying degrees of hardness. Depending on what part of the country you live in, you may have hard or soft water. Hard water may leave spots. Heated hard water will leave deposits behind. If the hard water is left sitting, it will break down the passive layer and rust stainless steel. All other water deposits, whether it be from food preparation or service, must be promptly removed.
Rust Prevention - Tools
Here are some best practices that can help prevent stainless steel rust when caring for stainless steel.
1. Use the proper tools and clean with the polish lines. When cleaning stainless steel products, use non-abrasive tools. Soft cloths and plastic scouring pads will not harm the steel passive layer. Use stainless steel pads, but the scrubbing motion must be in the direction of the manufacturer’s polishing marks. Some stainless steel comes with visible polishing lines or grain. When visible lines are present, always scrub in a motion parallel to the lines. If you cannot see the grain, play it safe and use a soft cloth or plastic scouring pad.
2. Use alkaline, alkaline chlorinated, or non-chloride-containing cleaners. Many traditional cleaners are full of chlorides, but the industry has provided an ever-increasing selection of non-chloride cleaners. If you are not sure of chloride content in the cleaner used, contact your cleaner supplier. If your present cleaner contains chlorides, ask your supplier if they have an alternative. Avoid cleaners containing quaternary salts since they can attack stainless steel and cause pitting and rusting.
3. Treat your water. Although this is not always practical, softening hard water can do much to reduce deposits. Install filters to remove distasteful and corrosive elements. To ensure proper water treatment, contact a treatment specialist.
Rust Prevention - Cleaning
- Keep your equipment clean. Use alkaline, alkaline chlorinated, or non-chloride cleaners at recommended strength. Clean frequently to avoid the build-up of hard, stubborn stains. If you boil water in stainless steel equipment, remember the single most likely cause of damage is chlorides in the water. Heating cleaners that contain chlorides have a similar effect.
- Rinse, rinse, rinse. In the event that you used chlorinated cleaners, rinse and wipe equipment and supplies immediately. The sooner you wipe off standing water the better, especially when it contains cleaning agents. After wiping equipment down, allow it to air dry; oxygen helps the passivity film when caring for stainless steel.
- Never use hydrochloric acid (muriatic acid) on stainless steel. If used, hydrochloric acid can cause cracking, corrosion, and pitting on stainless steel.
- Regularly restore/passivate stainless steel. See the recommended cleaners chart below.
Recommended Cleaners for Specific Situations
|Routine cleaning||Soap, ammonia, detergent, Medallion||Apply with cloth or sponge|
|Fingerprints & smears||Arcal 20, Lac-O-Nu Ecoshine||Provides barrier film|
|Stubborn stains & discoloration||Cameo, Talc, Zud, First Impression||Rub in direction of polish lines|
|Grease & fatty acids, blood, burnt-on-foods||Easy-off, De-Grease It Oven Aid||Excellent removal on all finishes|
|Grease & oil||Any good commercial detergent||Apply with sponge or cloth|
|Restoration/Passivation||Benefit, Super Sheen|