Stains concrete after rain
This worked well turning rust black and making a nice finish. My problem came after treating a metal railing.  After it dried a day and before I was able to second coat, rain came and stained my concrete around the railing black from what I am to assume was the converter product coming off the railing.  I was able to clean most of it off but it was inconvenient.  Note that this product is tannic acid based.  Some of the other converters also use organic acids of some sort.  I will try something else next time but it could be this is the nature of these products??
Rating: 3 stars