scrape away
1. To remove something (from some surface) with or as with the vigorous scrubbing of a rough, sharp, or hard-edged instrument. A noun or pronoun can be used between "scrape" and "away." He used a putty knife to scrape away the old paint from the wall. Stop scraping the scab away or you'll end up with a scar!
2. To scrub (something or some surface) vigorously with or as with a rough, sharp, or hard-edged instrument steadily or continuously. I sat there scraping away for nearly an hour, but the rust just wouldn't come off! She's up there scraping away at the gutter, trying to clear out all the moss and gunk that has been building up over the last year.