A friend picked up a stainless steel refrigerator for at a really great discount but it had some cosmetic damage from what seemed to be scotch tape and they are wondering how to clean or restore the surface.
In this case there is either chemical damage from the tape or whatever made those marks or there is physical damage to the surface. Most likely if you don’t see any scratches on the surface and the grain of the stainless looks uniform then the marks are either remaining glue or chemical damage.
The first thing you want to do is get the surface clean so this means using a chemical that will remove the adhesive. General purpose soap will often do the job and if not you might want to try acetone. Do not scrub hard just in case the damage is just residual glue.
The next thing you want to try if the surface still has problems is a stainless steel polish. Because Oxidation makes the surface look darker and the tape areas are lighter the tape probably removed the oxidation either through a chemical or physical reaction.
What you will need to do is polish the entire surface to bring that dark color back to the original light color where the tape was. Will take some work and you should rub in the direction of the grain of the stainless steel and not in circles or across the grain as you do it.
Once you are finished the refrigerator will be bright but over time it will oxidize and return to a darker color.
It is important to care for your stainless steel appliances and sinks with minimal scrubbing and you must always scrub in the direction of the grain and not against it.
With proper care your stainless will not normally discolor or have abrasive scratches from normal use.
Stainless is normally non reactive to chemicals but the oxidation is so this is why you get this discoloration. Never use harsh chemicals when cleaning they are not normally necessary.