Replastering - Strange "Rust Like" Spots on Gunite But No Rebar Anywhere Around

[KSP]

Replastering - Strange "Rust Like" Spots on Gunite But No Rebar Anywhere Around

Hello, new member here. I have what may be a problem in my pool and I could use some help in understanding it. I bought a house 5 years ago with an IG gunite pool and I have done my best to maintain it and keep the water chemistry in balance. With the plaster starting to get rough and a few small spots of plaster starting to flake I decide to get the pool replastered. When the plaster was removed I discovered some "rust like" blotches on the surface of the gunite. I chipped away a small section of the gunite but could not find any rebar. When I could find some rebar it was nearly a foot away from the spot and buried in gunite with no sign of rust. There are several of these spots on the surface of the gunite in my pool. If these are rust stains I do not know what cause them. Any ideas? I have attached a picture of one example, before I started chipping away at it.

Thanks

 

[YippeeSkippy]

Re: Replastering - Strange "Rust Like" Spots on Gunite But No Rebar Anywhere Around

Any chance of metal shavings having fallen in the pool in the past?

Just for grins and giggles, ask your local pool store to test for metals.

It sure looks like rust to me. Try holding some crushed Vit C tablets to the stain and see if that alters it some? Conversely if it doesn't, try a chlorine puck.

 

[KSP]

Re: Replastering - Strange "Rust Like" Spots on Gunite But No Rebar Anywhere Around

I tested the spots for metal and it turned out that they are rust. I am assuming when the previous owners last had it replastered the crew somehow left metal debris on the gunite surface and then applied the plaster over it.
Thanks YippeeSkippy for your help.