Hi Mike. Yes, it sounds like some sort of concentrated mineral slush was deposited. It can be a pain to remove successfully. Using a wet vac as you did before rinsing helps. Try a solution of one cup white vinegar to 1 gallon of warm water. Squirt some dish soap in the solution as well. Pour it on, let it sit a minute or two without drying out, scrub, and the use the wet vac to suck up the solution. Then rinse. This works fairly well sometimes for mineral deposits and salt residues in concrete.

Hi Mitch. If it’s concrete paint and not an actual coating (2-part epoxy, etc.) then you need to be careful using a pressure washer. Pressure washers work well for removing paint from concrete and you don’t want that to happen. If it’s paint on the concrete, then a 40° nozzle should be OK providing it does not get too close to the surface.

Hi Will. Something to consider is that any treatment that is performed on the surface of the concrete to remove the lines is not going to make it look like the surrounding concrete. You can remove those lines, but the color of the area treated may look lighter and have a slightly different look in texture as well. Coatings have a tendency to highlight differences in color tones and textures in concrete as well. Always start with the light and get progressively more aggressive as needed. A black pad is a good starting point. If that doesn’t do much, then you may need to start with a 150 grit sanding screen and get more aggressive from there if you need to. The sanding screen can be attached to the bottom of the black pad. Sanding screens and black pads will not polish the surface and won’t have an effect on how well TS210 adheres.