Add a little chromium, nickel and molybdenum to the usual mixture of iron and carbon during the smelting process, and you transform normal steel to stainless steel. The chromium in the mixture forms a protective layer of chromium oxide on the surface, and because chromium is super-hard, this layer of what's essentially chromium rust protects the material from scratches and stains.
Just as few things in the world are perfect, stainless steel isn't perfectly stain-proof. Among the household chemicals that can cause stains are strong acids, like vinegar and lemon juice, bleach, hard water and even salty water. It's also possible to scratch the chromium oxide layer, and if you do that, the metal underneath can rust.
All this means that your stainless steel cooktop needs care. Treat it well, and it will maintain its shine indefinitely, but treat it poorly, and it will look like, well, a stainless steel cooktop that has been treated poorly. A poorly treated appliance, such as a stainless gas cooktop, can often be restored, but not always. It depends on the severity of stains and scratches and the chemicals that caused the stains.
Removing Scratches From Stainless Steel
You should never use any type of abrasive material, such as steel wool or scouring powder, to clean stainless steel because they can scratch the surface. Scratches on a stainless steel cooktop can also be the result of normal kitchen activities, such as moving pots around or cutting vegetables.
If the scratches aren't too deep, you can rub them out with a soft cloth and a non-abrasive cleaning compound, such as Bar Keepers Friend. Apply a small amount of the compound to a rag and buff out the scratch, always rubbing in the direction of the polishing lines to avoid making the situation worse with cross-grain scratches. Rinse with clear water when you're done.
For deeper scratches, you'll probably need to purchase a stainless steel stove scratch remover kit, which has everything you need to get them out. The kit contains a set of appropriately abrasive pads, polishing compound and instructions on how to use them. You generally begin rubbing with a coarse pad and progressively graduate to finer ones until the scratch is gone.
Stainless Steel Cooktop Stain Removal
The most effective recipe for a stainless steel stain remover is a paste made from baking soda and dish soap. Several other things you find around the house also work, including mineral oil, club soda and even flour, but the baking soda/dish soap combination is probably the best.
Rub out stains with a soft cloth in the same way you rub out scratches, which is by going with the polish grain instead of against it. Don't apply excessive pressure, and don't move the cloth in a circular motion or you may leave streaks on the surface that are hard to remove. When the stains are gone, rinse everything with clear water and blot dry with a paper towel or soft rag.
Keep Your Stainless Steel Cooktop Looking its Best
Stainless steel is vulnerable to stains from chlorine and chlorides, which cause a permanent type of stain called pitting. Never expose stainless steel to bleach or any type of cleaner that contains bleach. Table salt is a chloride (sodium chloride) that can also damage stainless steel, although not as quickly as bleach. Never let salty water stand on a stainless gas cooktop.
To keep your cooktop free of potential staining compounds, rub it down weekly with a damp cloth and a non-abrasive cleaning compound. One manufacturer recommends spraying on a small amount of club soda and wiping it with the polish grain to keep the surface shiny and free of chemicals.