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
Why we say this
Strongly supported
CLOSED IN SPRINT 7, after four sprints of audit notes. The incompatibility is now stated by a document that was read: a safety data sheet naming aluminium under materials to avoid. Note precisely what changed and what did not. The COMPATIBILITY FACT is now directly evidenced, which is why this moves to strongly supported. The MECHANISM is not: the sheet gives no reaction, no product and no consequence, so the amphoteric account in the note above remains an interpretation from general chemistry and keeps a background citation rather than being promoted alongside it. Sprint 6 found the equivalent statement for sodium HYDROXIDE and declined to carry it across to carbonate; this is the carbonate-specific evidence that refusal required, and it was worth waiting for.
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)
Verification: a person has read the passage relied on.
Read on — Section 10.5, Incompatible materials. Supports a narrower statement — our claim was reduced. The incompatibility itself is now directly evidenced by a document that was read, and the sodium-carbonate-on-aluminium edge no longer rests on two unread reference works. What is NOT evidenced by it is the mechanism: the amphoteric-attack and hydrogen-evolution account remains an interpretation from general chemistry and is labelled as one. Sprint 6 found the equivalent statement for sodium HYDROXIDE and correctly declined to carry it across; this is the carbonate-specific source that declining required.
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)
Verification: the work exists and is described correctly. Nobody has yet read the specific passage.
Last reviewed by a person on .
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
Why we say this
Strongly supported
Read directly from the regulator's fact sheet in Sprint 6. The catalogue previously asserted the alkali-attacks-aluminium mechanism from an unread reference work; this states it, and adds the gas hazard that reference did not.
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)
Verification: a person has read the passage relied on.
Read on — The hazard rating panel and the Reactivity section. RE-READ IN SPRINT 6 from the PDF itself for the reaction-with-metals statement. Supports a wider statement — our claim was widened. Clears the last safety-bearing citation in the catalogue that rested only on unread sources: the alkali-attacks-aluminium edge now cites a regulator whose passage was read. It also supplied two things CleaningHQ did not have — that the reaction generates flammable and explosive hydrogen gas, which is a hazard rather than merely cosmetic damage, and that sodium hydroxide attacks COATINGS, which is the first read source behind the painted-and-coated-steel record.
Last reviewed by a person on .
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
- Recorded
- Alkalis
- Recorded
- Abrasion
- Recorded
- Porous
- Not applicable
“Not known” means CleaningHQ has not established this, not that the material is unaffected.
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
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)
Verification: the work exists and is described correctly. Nobody has yet read the specific passage.
What CleaningHQ cannot answer yet
These are recorded questions about this subject that we have not yet researched to a standard we would publish.
- Clean aluminium alloy road wheels
- Remove carbonised residue from bakeware
- Foil as an abrasive on barbecue grates
Last reviewed by a person on .