POR-15 soaked deep into the threads and broke up rust, leaving a clean area guiding. Similar to other rust removers, it darkens because it dissolves, turning black the more you utilize it. When you don't brain using a couple of precautions when working with this merchandise, it works well. https://tysondkpun.aboutyoublog.com/28923813/clean-rebar-rust-things-to-know-before-you-buy