Anodised aluminium
An oxide layer grown into the metal rather than laid on it. A standards body names five specific chemicals that must never touch it, and the damage is permanent.
What not to do
Trisodium phosphate is unsafe on Anodised aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
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 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)
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)
Hydrochloric 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
- Ventilate the area
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 hydrochloric acid must not be used on anodised surfaces. (states this directly)
In detail
Anodising converts the surface of aluminium into a thick, hard oxide that is part of the metal rather than a coating on it, which is why an anodised window frame, cookware body or appliance trim resists corrosion and abrasion far better than bare aluminium. The finish's chemical vulnerability is specific and a standards body names it. Aggressive alkaline and acid cleaners must never be used on aluminium finishes, and on anodised surfaces in particular, cleaners containing trisodium phosphate, phosphoric acid, hydrochloric acid, hydrofluoric acid, fluorides or similar compounds are prohibited. Between them, that covers a substantial share of the descaling, rust-treatment and heavy-duty cleaning aisle. The same guidance is unusually explicit that marks resulting from mistreatment MAY BE PERMANENT — there is no polishing an etched anodic layer back, because the layer is finite. Two further instructions matter. Cement and mortar corrode anodic coatings quickly if allowed to dry on the metal, which is a building-site problem that arrives with new windows. And cleaning must happen in the shade, because reactions on hot metal accelerate unevenly and streak the finish beyond restoring.
Properties
Sensitivity
- Acids
- Sensitive
- Alkalis
- Sensitive
- Chlorine bleach
- Not known
- Heat
- Sensitive
- Abrasion
- Sensitive
- Porous
- Not applicable
“Not known” means nobody has established this, not that the material is unaffected.
Why
- Anodised aluminium is explained by Corrosion and passivation
- Anodised aluminium is explained by Alkali attack on light metals
- Anodised aluminium is explained by Coating thickness
Related
- Anodised aluminium is commonly affected by Water marks
- Anodised aluminium is commonly affected by Dust
Aftercare and prevention
- Neutral cleaning requires the aftercare Anodised aluminium
Hacks and claims involving this
- Acidic wheel cleaner on alloy wheels Disputed
Sources for this page
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 aggressive alkaline and acid cleaners must never be used on aluminium finishes, that cleaners containing trisodium phosphate, phosphoric, hydrochloric or hydrofluoric acid or fluorides must not be used on anodised surfaces, that marks from mistreatment may be permanent, and that hot sun-heated surfaces must not be cleaned. (states this directly)