Phosphoric acid
A moderately strong acid used in descalers and rust treatments. The regulator's storage instruction names bleach among the things it must never meet.
What not to do
These are the combinations an authority has warned about. A substance nobody has warned about has not been cleared, and none of this is permission to mix.
Never mix
The regulator's instruction is that phosphoric acid must be stored to avoid contact with water, ammonia, BLEACH and nitromethane because violent reactions occur. Acid and hypochlorite together release chlorine gas, which is a severe respiratory irritant. In a bathroom the space is small and the concentration builds quickly. Leave the room, do not return to open a window, and seek medical advice.
Phosphoric acid is unsafe on Anodised aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
Evidence
Strongly supported
Sources
AAMA 609 & 610-02: Cleaning and Maintenance Guide for Architecturally Finished Aluminum
American Architectural Manufacturers Association (AAMA), 2002 · Standards body
Relied on for: That cleaners containing phosphoric acid must not be used on anodised surfaces and that marks from mistreatment may be permanent. (states this directly)
Phosphoric acid must never be mixed with Sodium hypochlorite (chlorine bleach)
Unsafe
Do not do this. The risk is established, and it is described below.
A regulator naming BLEACH by that word on the fact sheet for a substance sold to consumers as a descaler and rust treatment.
Precautions
- Never mix with other cleaning products
- Ventilate the area
- Wear gloves
- Wear eye protection
- Consider professional help
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Phosphoric Acid (RTK 1516)
New Jersey Department of Health, 2004 · Government or regulator
Relied on for: That phosphoric acid must be stored to avoid contact with water, ammonia, bleach and nitromethane since violent reactions occur. (states this directly)
Precautions
- Never mix with other cleaning products
- Wear gloves
- Wear eye protection
- Ventilate the area
- Rinse thoroughly afterwards
- Keep away from children and pets
In detail
Phosphoric acid sits between the weak organic acids of the kitchen cupboard and the strong mineral acids of the trade counter, which is why it does the work in a great many commercial limescale removers and rust treatments. The regulator's own summary of what it is for reads: rustproofing metals, fertilizers, detergents, foods, beverages and water treatment. On rust it does something the weaker acids do not — it converts iron oxide into iron phosphate, a stable dark film that adheres rather than flaking, which is why a bottle sold as a rust converter rather than a rust remover is usually built on it. It is corrosive, and contact can irritate and burn the eyes. The line that matters most in a bathroom is a storage instruction: it must be kept from contact with water, ammonia, bleach and nitromethane because violent reactions occur. A descaler and a bleach-based cleaner are commonly used on the same tiles within minutes of each other, which is precisely the situation that instruction describes. The same sheet also says to store it away from glass, rubber, plastics and coatings.
Properties
- Chemical name
- Orthophosphoric acid
- pH
- Strongly acidic
What works
Phosphoric acid is effective against Limescale Supported
Phosphoric acid is effective against Rust Supported
It converts rather than removes, which is why a treated surface goes dark rather than clean.
Why
- Phosphoric acid is explained by pH in cleaning
- Phosphoric acid is explained by Corrosion and passivation
Hacks and claims involving this
- Pouring cola into a toilet to clean it Unresolved
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Phosphoric Acid (RTK 1516)
New Jersey Department of Health, 2004 · Government or regulator
Relied on for: That phosphoric acid is used in rustproofing metals, detergents and water treatment, that it is corrosive, and that it must be stored to avoid contact with water, ammonia, bleach and nitromethane since violent reactions occur. (states this directly)