I'm not CNKS but I'm a very satisfied Picklex 20 user. Coverage is 200 SF
per pint. It's great stuff. Well worth the price. If you're going to use a phosphoric acid product, this is the one to get. However, I suggest you remove the vast majority of rust by other means. Don't rely on Picklex 20 to do everything. When it comes to rust, there is no "quick fix" miracle product.