I have a pool 40 ft x 20ft irregular shape about 10 years old which is at our house in Southern France. It was constructed with a reinforced concrete structure with a sprayed marble cement surface finish.
About 2 years ago we noticed 2/3 small rust marks which we think was caused by a small pieces of the mild steel wire joining the reinforcing bars together coming into contact with pool water. Originally we used a salt water generator for chlorine production but have since stopped using because we thought that this was making the rust problem worse; we now use slow release chlorine
To solve the original rust problem we drained the pool, cut out the the rust areas and patched the surface. This was successful on the original patch but since then another rust spot has appeared - this time on the side of the pool - leaving a stain 14 inches x 2inches)
I need advice
Can the rust mark be sealed using an epoxy putty rather than draining the pool again? ( fairly expensive in our part of the world)
and can the stain be removed using Ascorbic Acid or Citric Acid?
Any advice really appreciated