Are your blades developing the rust patches because of old age, and because of many previous sharpening sessions have removed most of the case-hardening of the outer coating of the blade, so that the only metal in the blade that is left is the soft metal ? I had blades that looked like yours do, and was still able to skate on them. However, the blades needed even more sharpening because the soft metal would not hold a sharp edge for very long. You can have the blades tested with a measuring device to see if the case-hardening has all been removed, and to see if the blades are near or have reached the end of their useful life.