Strange spots on my blade

[FatFrumos]

Hello.  I'm finishing up my second kitchen knife.  It's made out of AEB-L and I wanted to apply a satin to it, so I sanded one part down to 1000 grit, then covered it with a masking tape, flipped it over and did the other side.  When I took the tape off, I discovered white spots on the blade that you can see in the picture.  I tried to sand them off (but I didn't go lower than 400 grit) and wash them off with acetone, but to no avail.  What can they be, any ideas?  The only thing I can think of is they are gouges left by some large steel crumbs, but why are they pits and not scratches and how did they make it so deep under the masking tape? If anyone has any suggestions, I'd be very grateful.

Thank you!

Luka

[DuEulear]

Only a guess but it is possible the tape you are using is slightly acidic and reacted with part of tge steel etching a particular alloy element and none of the others? 

 

I know nothing of that alloy but is the only idea i can think of 

 

susan

[rhitee93]

Something has reacted with it, but you may never know what.  I don't like to stick tape on my blades for any operation where they get wet because this sort of things always seems to happen.  (I am assuming you are wet sanding)

When I get up to the higher grits, and need to flip the blade, I just wipe down the surface of the board I have the blade on, and fold up a clean piece of paper towel to lay between the blade and the board.

I also used glass cleaner rather than water when sanding.  It doesn't cause rust as fast.

[FatFrumos]

This is unexpected.   Just to clarify my process - I do not use water, I use WD40 and wipe the side with acetone prior to taping it up.  But I guess I won't be taping them up any more, or at least wrap them in paper before taping.  But anyways, you leave, you learn.  Thank you very much for your responses!