Rust spot on plaster

[Rockcrawler]

Not sure where I was supose to post this one, I noticed today while vacuuming my pool that I have a small rust spot, size of pencil eraser, but very noticable, it looks like it was from an object rather than a chemically induced stain. What is the best way to remove the stain, it is on plaster.

Thanks

Rob

 

[JohnT]

Vitamin C tablets are great rust removers. If it's on the floor, just lay the tablet on the spot (easier said than done). If it's on the wall, rub the spot with the tablet.

Before doing anything, examine the spot closely to be sure it isn't rebar installed too close to the surface.

 

[Rockcrawler]

Thanks John, man if its rebar then there is a real problem

 

[AV8TOR]

Before doing anything, examine the spot closely to be sure it isn't rebar installed too close to the surface.

Interesting - what do you do then?

I have heard of the wire ties that that twist the rebar together poking through.

 

[budster]

Before doing anything, examine the spot closely to be sure it isn't rebar installed too close to the surface.

Interesting - what do you do then?

I have heard of the wire ties that that twist the rebar together poking through.

I might rephrase the above statement. The rebar would not have been installed to close to the surface, the shotcrete or gunite and plaster would have been applied too thinly over that rebar.

If that were the case, or if a tiewire was poking through, it would require some plaster repair. If the surface is just white plaster, it would be easier than if it were a premix color, or an aggregate mix finish. All doable, though.

 

[AV8TOR]

So can you skim coat over the existing plaster then?

 

[budster]

So can you skim coat over the existing plaster then?

Are we talking white marcite finish? If so, as long as you can get a product that bonds with the existing plaster, it is possible. I'd defer to one of the plaster experts on this forum. This is not my area, but I can do some quick research on products that claim to fix this problem. BRB.

On Edit: A hydraulic cement can be used to plug any holes, etc., but this repair product category is not the same as the plaster. I'd consult a better tech source.

 

[Curmudgeon]

Oxalic acid works well as a rust remover. Sold as Bar Keepers Friend.

I would test it on an out of the way piece of plaster first.

It is a great rust remover for tools. Does not attack iron or steel.


Curmudgeon

350 gal at 103 *F.
HTH, muriatic acid, sodium bicarbonate, and borax