Trisodium phosphate
A heavy-duty alkaline cleaner and water softener, used before painting. It is a builder as much as a cleaner, and it corrodes aluminium and brass.
What not to do
Trisodium phosphate is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
- Ventilate the area
Why we say this
Strongly supported
Two independent authorities: a state health department on the reaction, and a standards body naming this compound specifically among those prohibited on an aluminium finish. That is as well-corroborated as a material warning gets here.
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate in water solution reacts with aluminium, zinc and galvanised iron to produce flammable hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' paragraph and the 'HANDLING AND STORAGE' reactivity list. Supports the claim as stated. Adds the alkaline builder family to the agent records, and gives the catalogue a fourth independent regulator statement that alkalis attack aluminium — which is now sourced from sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium carbonate rather than from one sheet.
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 trisodium phosphate must not be used on anodised aluminium surfaces. (states this directly)
Verification: a person has read the passage relied on.
Read on — Read in full. Sections 3 General, 4.1 light surface soil, 4.3 organic coatings, and 5 Cleaning Precautions. Supports the claim as stated.
Last reviewed by a person on .
Trisodium phosphate is unsafe on Anodised aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Why we say this
Strongly supported
A standards body naming the compound and the finish together, with the permanence of the damage stated in the same document.
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 trisodium phosphate, phosphoric acid, hydrochloric acid, hydrofluoric acid or fluorides must not be used on anodised surfaces, and that marks from mistreatment may be permanent. (states this directly)
Verification: a person has read the passage relied on.
Read on — Read in full. Sections 3 General, 4.1 light surface soil, 4.3 organic coatings, and 5 Cleaning Precautions. Supports the claim as stated.
Last reviewed by a person on .
Trisodium phosphate is unsafe on Galvanised steel
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Ventilate the area
Why we say this
Strongly supported
Named metal, named reaction, named gas.
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate solutions react with galvanised iron to produce flammable hydrogen gas. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' paragraph and the 'HANDLING AND STORAGE' reactivity list. Supports the claim as stated. Adds the alkaline builder family to the agent records, and gives the catalogue a fourth independent regulator statement that alkalis attack aluminium — which is now sourced from sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium carbonate rather than from one sheet.
Last reviewed by a person on .
Precautions
- Wear gloves
- Wear eye protection
- Rinse thoroughly afterwards
- Never mix with other cleaning products
- Keep away from children and pets
In detail
Trisodium phosphate is the strong alkaline powder decorating guidance reaches for when a wall has to be degreased before paint will key to it, and the sugar-soap products sold in Britain for the same job are close relatives. The regulator's use sentence explains why it does two apparently unrelated things: it is a water softener, a detergent ingredient and a paint remover. Softening and cleaning are the same property here — the phosphate binds the calcium and magnesium that would otherwise tie up the surfactant, which is what a builder does in a laundry powder, and the resulting alkalinity saponifies greasy soil directly. The powder itself feels innocuous, and the storage instruction is the tell: keep it away from water and moisture, because caustic solutions may be formed. The caustic appears when it dissolves, not in the tub. Its metals list is the standard alkaline one and it is specific — in solution it reacts with aluminium, zinc and galvanised iron to produce flammable hydrogen, and it may corrode brass and steel when wet. Phosphate content is restricted in domestic detergents in many countries, so a British product under a similar name may not be this compound.
Properties
- Chemical name
- Sodium phosphate, tribasic
- pH
- Strongly alkaline
What works
Trisodium phosphate is effective against Grease Supported
Why
- Trisodium phosphate is explained by pH in cleaning
- Trisodium phosphate is explained by Builders and water softening
- Trisodium phosphate is explained by Alkali attack on light metals
Sources for this page
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Phosphate, Tribasic (RTK 1724)
New Jersey Department of Health · Government or regulator
Relied on for: That trisodium phosphate is used as a water softener, in detergents and as a paint remover, that its solutions react with aluminium, zinc and galvanised iron to produce hydrogen, that it may corrode brass and steel when wet, and that caustic solutions may be formed on contact with water. (states this directly)
Verification: a person has read the passage relied on.
Read on — The 'IDENTIFICATION' paragraph and the 'HANDLING AND STORAGE' reactivity list. Supports the claim as stated. Adds the alkaline builder family to the agent records, and gives the catalogue a fourth independent regulator statement that alkalis attack aluminium — which is now sourced from sodium hydroxide, potassium hydroxide, trisodium phosphate and sodium carbonate rather than from one sheet.
Last reviewed by a person on .