Aluminium
Protected by its own oxide layer, but amphoteric: attacked by strong alkalis as well as strong acids, which rules out many oven and dishwasher products.
What not to do
Sodium carbonate is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Aluminium is amphoteric: strong alkali dissolves the protective oxide and then attacks the metal, leaving a dull grey or blackened surface that is not a deposit.
Precautions
- Wear gloves
- Test on an inconspicuous area first
Evidence
Strongly supported
Sources
Safety Data Sheet: Sodium Carbonate
Murphy and Son Ltd · Manufacturer documentation
Relied on for: That the supplier's safety data sheet lists ALUMINIUM among the materials to avoid for sodium carbonate, under section 10.5, Incompatible materials. (states this directly)
Kirk-Othmer Encyclopedia of Chemical Technology
John Wiley & Sons · Reference work
Relied on for: That aluminium is amphoteric and that its protective oxide film is dissolved by strong alkali. (background and mechanism only)
Sodium hydroxide is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Not only surface damage. The regulator's sheet states the reaction produces flammable and explosive hydrogen gas — which is what caustic oven cleaner on an aluminium tray does inside a closed oven.
Precautions
- Ventilate the area
- Wear gloves
- Wear eye protection
- Never mix with other cleaning products
- Keep away from children and pets
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Sodium Hydroxide
New Jersey Department of Health, Right to Know Program · Government or regulator
Relied on for: That sodium hydroxide reacts with metals such as aluminium, lead, tin and zinc to form flammable and explosive hydrogen gas, and that it is a highly corrosive chemical causing severe skin and eye burns. (states this directly)
Potassium hydroxide is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
The reaction gives off hydrogen, which is flammable. This is a hazard as well as a damage warning.
Precautions
- Ventilate the area
- Wear gloves
- Wear eye protection
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Potassium Hydroxide (RTK 1571)
New Jersey Department of Health, 2010 · Government or regulator
Relied on for: That potassium hydroxide is corrosive in moist air to aluminium, zinc, tin and lead and forms flammable and explosive hydrogen gas. (states this directly)
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
Evidence
Strongly supported
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)
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)
Ammonia is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Ventilate the area
- Wear gloves
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Ammonium Hydroxide (RTK 0103)
New Jersey Department of Health, 2011 · Government or regulator
Relied on for: That copper, aluminium and galvanised metals must not be used when handling ammonium hydroxide. (states this directly)
Dishwasher detergent is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Evidence
Supported
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 alkaline phosphate solutions react with aluminium to produce hydrogen and corrode it. (applied to this case rather than stated directly)
Care and Maintenance: Caesarstone Surfaces
Caesarstone Ltd. · Manufacturer documentation
Relied on for: That dishwasher detergent is on the manufacturer's prohibited list for a hard surface because of its aggressiveness. (states this directly)
Oven cleaner 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
Evidence
Supported
Sources
Right to Know Hazardous Substance Fact Sheet: Potassium Hydroxide (RTK 1571)
New Jersey Department of Health, 2010 · Government or regulator
Relied on for: That potassium hydroxide is corrosive in moist air to aluminium, zinc, tin and lead, forming hydrogen gas. (states this directly)
Care and Maintenance: Caesarstone Surfaces
Caesarstone Ltd. · Manufacturer documentation
Relied on for: That oven and grill cleaners are prohibited by the manufacturer on its surfaces. (states this directly)
Perchloroethylene is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Ventilate the area
- Wear gloves
- Consider professional help
Evidence
Strongly supported
Sources
Right to Know Hazardous Substance Fact Sheet: Tetrachloroethylene (RTK 1810)
New Jersey Department of Health, 2011 · Government or regulator
Relied on for: That tetrachloroethylene reacts violently with finely dispersed or finely divided metals including aluminium. (states this directly)
Sugar soap is unsafe on Aluminium
Unsafe
Do not do this. The risk is established, and it is described below.
Precautions
- Wear gloves
- Wear eye protection
- Rinse thoroughly afterwards
Evidence
Strongly supported
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 and may corrode brass and steel when wet. (states this directly)
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 surfaces. (states this directly)
Precautions
- Test on an inconspicuous area first
- Check the manufacturer's instructions
In detail
Aluminium forms a tough oxide layer almost instantly on exposure to air, and that layer is why a reactive metal behaves like a stable one in ordinary use. The complication for cleaning is that aluminium is amphoteric — it reacts with strong bases as well as strong acids. Strongly alkaline cleaners, which includes many oven cleaners and heavy-duty degreasers, dissolve the protective oxide and then attack the metal, characteristically leaving a dull grey or blackened surface that is not a deposit and cannot be cleaned away. This is the mechanism behind the standard warning against putting aluminium pans through a dishwasher, where alkaline detergents act on them over a long hot cycle. Anodised aluminium has a thickened, dyed oxide layer that is more durable but is itself damaged by the same alkalis, and once the anodising is breached the appearance cannot be restored by cleaning.
Properties
Sensitivity
- Acids
- Sensitive
- Alkalis
- Sensitive
- Abrasion
- Sensitive
- Porous
- Not applicable
“Not known” means nobody has established this, not that the material is unaffected.
Why
- Aluminium is explained by Alkali attack on light metals
Hacks and claims involving this
- Ash and water on stove glass Supported
- Aluminium foil for surface rust on chrome Established practitioner practice
- Vinegar as an all-purpose cleaner Disputed
- Using a dishwasher tablet outside the dishwasher Unresolved
- Oven cleaner for a stubborn worktop mark Does not work
- Using oven cleaner in a self-cleaning oven Does not work
- Decanting bleach into another container Does not work
- Lining hob drip pans with foil Does not work
- Washing soda as a general-purpose cleaner Disputed
When the obvious answer is wrong
Can I use oven cleaner or a strong degreaser on aluminium?
Aluminium is amphoteric — attacked by strong bases as well as by strong acids. The alkali dissolves the protective oxide film and then the metal beneath, leaving a dull grey or blackened surface that is not a deposit and cannot be cleaned off. There is a second consequence that is a safety matter rather than a cosmetic one: a US state hazardous substance fact sheet records that sodium hydroxide reacts with metals including aluminium to form flammable and explosive hydrogen gas, which is not what anybody expects from cleaning an oven tray in a confined space.
A different kind of treatment works: Take the contact-time route instead of the chemical-strength route. Soaking in hot water with an ordinary detergent softens polymerised soil given long enough, and repeating a mild treatment is the trade's stated sequence for burnt-on deposits precisely because the aggressive alternatives damage surfaces. Where the item is unquestionably steel rather than aluminium the caustic route is available, so the first thing worth establishing is which metal you have — aluminium trays and steel trays look similar and behave completely differently. If a caustic product has already been used, ventilate and do not enclose the item while it is reacting.
Sources for this page
Sources
Kirk-Othmer Encyclopedia of Chemical Technology
John Wiley & Sons · Reference work
Relied on for: That aluminium is amphoteric and that its corrosion resistance depends on a surface oxide film attacked by strong alkali. (background and mechanism only)