Some advise - use a toothpick and vinegar to remove it. Remove the vinegar afterwards. Use iso alcohol to remove. Be careful around traces. I found a toothbrush to be too abrasive for trace heavy areas. Also I tried acetone - I think it was a little too strong. It worked but I've got some areas where the traces are exposed (mask has worn off). So my advise would be vinegar and a toothpick for the heavy stuff. Maybe a toothbrush for lighter stuff. Compared to mine, yours doesn't look that badly damaged... Once you get the heavy stuff off you'll probably see that the traces are mostly still intact.
Of course my one board with a leaked maxell battery would be the one board I have that didn't have any electrolytics on it...
Of course my one board with a leaked maxell battery would be the one board I have that didn't have any electrolytics on it...