Removing 50 yrs of mineral scum from sink - muriatic acid?

[AcidWater]

I need to pull the bathroom sink to replace the putty so will replace the worn out valve set as well. So I can take the stripped sink outside. The scum is copper "green blue" and pretty thick. Mostly dripped down from the hot tap. What's the best chemical? If muriatic acid, I know that I'll have to be careful to keep away from the bare iron bottom & not to undermine the adhesion at the transition from the glass to iron boundary.

BTW I don't know if this is ceramic or porcelain, how do you tell the difference?

No new sink , its part of a pair in the hall bath.

 

[WorthFlorida]

You’ll probably will dull and etch the porcelain with muriatic acid. You can try CLR and let it soak a few hours. Check with a pool supply store. They sell stain removers for metal stains on pools.

Call on those that refinished bath tubs. They do use an acid wash that etches surface but I do not know what kind. After the prep the sink it can be sprayed with an extremely hard finish that looks new. Your other sink must be in the same condition.

 

[Sponsor]

 

[Jadnashua]

If the sink is glazed, that layer on top is essentially glass. A porcelain sink is pottery with a glass based glaze on it. Otherwise, if it’s metal, the base may be cast iron. A magnet is a quick check if you can’t see the bottom easily.

 

[JohnCT]

The scum is copper "green blue" and pretty thick. Mostly dripped down from the hot tap.

I'm in the same boat (well, tub..). Before I added an acid neutralizer to my well, I was leaching copper until I started sprouting pin holes. My tub though is a fiberglass enclosure, and I don't know how to get the green off either. Whatever will ultimately work will have to dissolve the copper residue.

My brother is a chemist and he suggested white vinegar. I haven't tried that yet. Should be safe for fiberglass.

John

 

[AcidWater]

You’ll probably will dull and etch the porcelain with muriatic acid. You can try CLR and let it soak a few hours. Check with a pool supply store. They sell stain removers for metal stains on pools.
.

What is CLR?

 

[AcidWater]

Oh, my wife has some stuff called Clean Shower, it has mildewcide (B.A.C. - benzyl ammonium choloride) but no ingredients that will dissolve hard mineral deposits

 

[Jadnashua]

What is CLR?

CLR is a brand name. It is essentially acid. A stronger one than vinegar, and weaker than muriatic.

 

[AcidWater]

do you mean "CLR® CALCIUM, LIME & RUST REMOVER" ? looking up the MSDS for that...

https://clrbrands.com/en-US/Products/CLR-Household/CLR-Calcium-Lime-Rust-Remover

Directions:
In a well-ventilated area, mix equal amounts of CLR and warm water. Test on a hidden area before applying to the entire surface, Apply directly to the stain with a brush, cloth, or sponge. After 2 minutes, rinse promptly with cold water. Never leave CLR on an area for longer than two minutes. Never mix CLR with other household cleaners or bleach. Always read the manufacturer's directions of the item you will be cleaning to make sure that this product is compatible. Consumer discretion is always advised.

CLR may etch older sinks, tubs, and tiles. Avoid contact with wood, clothing, wallpaper, and carpeting. Some laminated surfaces (counter tops) are coated with a synthetic surface which may be affected by rust removes; clean spills immediately.

Ingredients
Lactic Acid
Lactic acid is found in many yogurts and cheeses. It is also produced in the muscles during intense activity. Commercially, it is produced by fermentation of simple sugars. In cleaning producs it functions as a chelating agent; a compound that makes metals more soluble in water. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients
Lauramine Oxide
Name for a surfactant. Is used in cleaners to modify the surface tension of water, to aid in even spreading and to allow mixing with oil and dirt so that they can be rinsed away; it is included in many soaps, detergents, and several groups of antiseptics. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients.
Gluconic Acid
This ingredient is an acid formed from the sugar glucose, which naturally occurs in fruit, honey and wine. It is a chelating agent; a compound that makes metals more soluble in water. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients.
Tripropylene Glycol n-Butyl Ether
Name for a solvent used to slow down the evaporation of many liquid products including oven cleaners and inks for ball-point and felt-tip pens. It is very effective at absorbing organic material. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients.
Yellow No. 5
A synthetic lemon yellow dye used all over the world, primarily as food coloring. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients.
Blue No.1
A blue dye used for foods and other substances. As part of the EPA Safer Choice Program, it has been evaluated and determined to be safer than traditional chemical ingredients.
Water
Reverse Osmosis (RO) is a water treatment process that removes contaminants from water by passing the water through a membrane, (filter), where contaminants are filtered out yielding more pure quality water.

 

[AcidWater]

Seems that these products use a weak acid and a politically correct chelating agent to sequester the metal once dissolved.
I think I will try TSP (trisodium phosphate).

 

[AcidWater]

This is working. Got rid of lesser stain under cold tap -- just one flake remains, may need a dental pick. Hot tap is 75% gone, just the thickest area remains.

Take lemon juice & heat it up hot. Close drain. Dip strips of paper towel in juice & apply to vertical surfaces as a moulage. Make sure ends of strips reach bottom of sink. Now add a couple teaspoons of TSO to the juice. It will foam up. Actually I don't have any TSP that I can find, so using Alconox laboratory glass cleaner, which is a phosphate based detergent/chelating agent. Mix it in, then pour it over the moulage so you have acid + chelating agent. The excess at the bottom will wick up the paper towels. Cover the sink to prevent evaporation. Let it sit "a while" ( I ate dinner) then peel it off & scrub with a phospher bronze (soft) brush. Re-apply moulage & repeat wetting & soaking with fresh solution.

 

[AcidWater]

I have to call this a success after soaking overnight. Had to scrape thickest remainder with a razor blade, but it kind of popped off mostly.

 

[JohnCT]

I have to call this a success after soaking overnight. Had to scrape thickest remainder with a razor blade, but it kind of popped off mostly.

You inspired me to get back to my stained fiberglass tub. I used some white vinegar and salt, and it's slowly dissolving the green crud. I can feel the thickness of it in places so this is going to take some time. Because it's fiberglass, I won't have the advantage of using any sort of abrasive or any other physical persuasion to hasten the process. Glad you got yours done.

John