The amount of material required if using our 100% solids coatings for 100 sq. ft would be 2.81 gallons if applying at 45 mil (the thickness of standard EPDM).
Most DIY coatings are not 100% solids and are similar to paint with respect to durability since they are designed to dry, not cure.
To best advise you regarding the deteriorating concrete, some photos would be helpful, but in general, our coatings consist of both liquid parts (part A and B), and a powdered component which allows you to thicken it for rapid build on the verticals and also to trowel if needed to fill voids. Since the product cures, there is no issue with thick applications such as would be encountered in a product which dries.
Cure times vary depending on how thick (thick application cures faster, not slower), how much (if any) lacquer thinner is used, and the temperature (ambient and surface). In general, at 80 degrees, expect a working pot life once the A and B are combined of about 20 minutes, the wait time for second coat (if needed for verticals) of 2 – 4 hours, 80% cure of 8 hours. Basically, the pond could be but in service the morning after application, but we advise waiting at least 48 hours for maximum cure.
Cost is dependent on the actual product selected, and what percentage of powder to liquid is best for your specific needs. Most pond and water feature applications are custom quoted since there is no one size fits all which is reliable and cost effective. For 3 gallons, the cost including shipping to most U.S. locations could vary from $242 – $477 depending on actual product and formulation you select