A reader wants to get rid of chemical marks from oven cleaner on a stainless-steel sink. (Reader photo)

Q: I was cleaning stainless-steel oven racks one day, using Easy-Off to loosen grime. I put the racks in my stainless-steel kitchen sink and left them there too long. Now my sink is all marked up from the chemicals in the cleaner. I looked for solutions online. One recommendation was brass polish, which I've tried, but the sink still looks awful. Is there anything I can do to restore the sink, or does it need to be replaced?

Falls Church

A: Try rubbing the sink with a maroon Scotch-Brite pad and a cleanser such as Bar Keepers Friend or Bon Ami, suggests Noreen Hansen, who is in charge of consumer and technical information for Elkay, a manufacturer of stainless-steel sinks and other products. You can substitute other powdered cleansers as long as they don’t contain chlorine bleach.

Rub only in the direction of the grain brushed into the stainless steel, not in a circular motion, except around the drain, where you have no other practical option. “Rinse really well,” Hansen said. “Wait a couple of days and do it again.”

Hansen recoiled at the idea of using oven cleaner on a stainless-steel sink. “Caustic chemicals are not okay, not on stainless steel,” she said. “Not even bleach.” Elkay even warns against storing open containers of household cleaners and chemicals containing chloride such as bleach, acid, drain cleaner and toilet bowl cleaner beneath the sink. Vapors from the chlorides can pit and corrode stainless steel, the company’s website warns.

Yet Easy-Off Heavy Duty Oven & Grill Cleaner, which comes in a yellow can, and Easy-Off Professional Fume Free Oven Cleaner, which has blue labeling, are marketed suitable for use on stainless steel. Labels on both products state: “Ideal for cleaning ovens/oven doors, broilers/broiler pans, and stainless steel surfaces.”

Two people who answered calls to the customer-care number for Easy-Off and its parent company, Reckitt Benckiser, said the problem is that oven cleaner is safe only for stainless steel inside an oven. On the exterior, oven cleaner can cause damage if the manufacturer saved money by adding only a thin layer of stainless steel over parts mostly made of ordinary steel. Oven cleaner can strip this plating, ruining the appearance, they said. Asked for advice about how to deal with damage to a stainless-steel sink, both referred the calls to the company’s public relations staff, who had not responded after two days.

The caution against using oven cleaner outside an oven isn’t immediately obvious from the product labels. The heavy-duty cleaner’s label does warn against using it on exterior oven surfaces, but doesn’t elaborate. The fume-free cleaner’s label has no such warning. And neither label offers clear advice about how to clean oven racks, including ones made of stainless steel. The heavy-duty cleaner’s label says to remove racks for cleaning separately, but it doesn’t give specifics. The fume-free cleaner’s label shows an oven rack in place as the cleaner is being sprayed on, but the FAQ section of the brand’s website, easyoff.us, is more cautious: “EASY-OFF Fume Free Oven Cleaner is safe for oven racks, but if the racks have plating on them, it may cause flaking or peeling, and possible staining.” Nowhere is there a warning against setting racks into a stainless-steel sink for cleaning — despite the fact that the main labeling says the cleaners are safe to use on “stainless steel surfaces.”

In fact, caustic solutions and even caustic vapors can cause stainless steel to rust. “It is ‘stain-less’ not ‘stain-impossible,’ ” notes the website of the British Stainless Steel Association. Stainless steel always contains both ordinary, rust-prone steel and chromium, with other ingredients such as nickel often added for luster or other qualities. The chromium is what offers the protection against rust. The way it does that isn’t what you might expect: The chromium at the surface combines with oxygen, forming a protective blanket of chromium oxide that keeps oxygen in the air or water from combining with the steel molecules and forming iron oxide, also known as rust. One beauty of the way this works is that the chromium oxide layer is self-healing: If it’s scratched, new chromium oxide forms and protects the underlying stainless steel. So scrub away on stainless steel. It’s not like lacquer or another surface coating where a scratch or a worn spot lets rust begin. And the chromium oxide layer is smooth; rust on steel is rough and can build up enough to flake off.

However, certain chemicals or conditions can interfere with the self-healing ability of stainless steel. Cleaning a stainless-steel sink with chlorine bleach strips off the chromium oxide layer, and if you use a steel-wool scrub pad at the same time, you set up perfect conditions for rust to form. Bits of the steel wool will probably remain on the surface, caught in crevices in the finish. These bits will not only rust but can also reduce the concentration of chromium in proportion to steel at the surface, keeping a new chromium oxide layer from forming.

Placing a rubber mat in a stainless-steel sink can also cause problems because the rubber sticks to the surface, keeping the protective layer of chromium oxide from forming. Racks that let air circulate underneath work fine, though.

Luckily, stainless-steel sinks are solid stainless all the way through. So if you work at it and can scrub away the rust, your sink should be primed for a new coat of its own protective finish.