Thank you for your question.
There seem to be a number of "recipes" for removing rust stains from
porcelain. here are a few you could try:
Does anyone know how to get rid of rust stains on a porcelain bath
tub? My daughter left a can of shaving soap on the rim and it left
rest stains which I cannot remove. I have tried bleach, scouring
powders with bleach, and baking soda with peroxide,
This works great! Pour a pile of table salt on top of the rust spot
then squeeze lemon juice over it. Let this pile of salty lemon juice
sit for several hours, over night or longer. This will draw the stain
out and you can actually see the rust in the pile of salt when its
down its job.
To get rid of rust stains in a tub or toilet, just rub gently with a
pumice stone. Works like a charm.
Whisk It Out
An excellent product that I have used to get out rust stains is called
Whisk Rust Stain Remover. The bottle says that it will get rust stains
off white sinks and toilet bowls. Both are porcelain, so this product
should work on your porcelain tub. The product produces a chemical
reaction, which removes the rust. I have used this on clothes with
rust stains, and it was successful every time I have used it. This is
an wonderful product!
Donna from California.."
There are more suggestions on this page including Naval Jelly, The
Works and Barkeeper's Friend.
The Natural Handyman recommends oxalic acid and more:
"...Red, reddish brown (from rust or iron)
Paste of borax and lemon juice; let dry, then rinse
Paste of mild scouring powder, cream of tartar, peroxide; let stand
1/2 hour, then rinse
Trisodium phosphate in water, then rinse
Commercial products (like ZUD), then rinse
Oxalic acid, 1 part to 10 parts water, then rinse..."
The Frugal Life says:
"...There's a product I bought in Houston, Texas that I will never be
without. Everyone who comes to visit us is first requested to pick up
a bottle of this magic potion. We have not been able to locate it in
Colorado. The product is called The Original Quaker House Rust & Stain
Remover: for fabrics, toilet bowls, metals, urine stains, sinks, and
carpets. I keep it by my sink because it will eliminate coffee stains
or any other food stains on my white ceramic sink, immediately. For a
true rust stain, I have the same result. Within seconds, the stain is
gone. I've also taken a whole bottle to a toilet bowl that someone was
trying to clean from years of hard water. Amazing...cleaned it within
seconds, whereas the owner had scrubbed for hours with a variety of
cleaners. All that is written on the bottle is that it's by Quaker
Cleaners in Houston, Texas. No Website is listed or address. Hope that
helps. Marcia Horn Noyes..."
LookSmart has an article with more suggestions:
"...Remove rust from toilet
To make your toilet bowl clean again, start with a dry bowl so water
won't dilute the cleaner. To tackle difficult rust stains, skip your
discount-store toilet bowl cleaner and head to the hardware store for
a product containing diluted hydrochloric acid (also listed on product
labels as hydrogen chloride, HCL or muriatic acid). This is a common
active ingredient in such brands as The Works Toilet Bowl Cleaner and
Santeen De-Limer & Toilet Bowl Cleaner (see Buyer's Guide, p. 76.) And
make sure you don't use a bleach-containing product on rust--it will
set the stain.
Be sure to use a toilet brush with stiff nylon bristles in a plastic
base. Those old wire brushes scratch the bowl. Once the bowl surface
becomes scratched or worn, stain removal becomes next to impossible.
Two cautions when cleaning with diluted hydrochloric acid. First, if
you use an in-tank cleaner that contains bleach, remove it and flush
multiple times to remove bleach residue. A combination of
bleach-containing and acid-containing products (toilet cleaners)
produces deadly vapors.
Second caution: Scrub slowly because droplets that splatter outside
the bowl can harm carpet, tile, vinyl and your skin. Keep a rag and a
bucket of water handy to wipe up spatters. Same goes for setting the
bottle down on these surfaces--don't. And make sure you flush and
rinse the bowl immediately..."
Whink has a product for this pupose called "Rust Flush"
"Whink® Rust Flush? dissolves rust
& hard water stains ... Fast!
This toilet bowl cleaner from Whink® effectively dissolves rust & hard
water stains from toilet bowls. Special thickening agents allow Rust
Flush? to cling to bowl sides and work more effectively.
Rust Flush? is also effective for rust stains and hard water build-up on sinks,
tubs, showers, tile and glass.
This formula is also safe for use on colored fixtures, porcelain,
fiberglass fixtures or stainless steel fixtures..."
As you can see, there are numerous suggestions to be found. If you
would like more, you can repeat my search here:
toilet +rust stain
I trust my research has provided you with useful suggestions to clean
your rust stains. If a link above should fail to work or anything
require further explanation or research, please do post a Request for
Clarification prior to rating the answer and closing the question and
I will be pleased to assist further.