Prep first
Before you start
- Fix the water source first, and dry the metal completely within 24 to 48 hours.
- Protect your lungs, skin and eyes before you touch the mold.
- Brush loose mold off outdoors if you can, so spores don't scatter indoors.
- Porous items may have to be thrown away, but a solid metal surface can usually be cleaned.
A patch of mold on metal usually means moisture is hanging around nearby, and the fungus only keeps going while that moisture stays. Recent growth wipes away far more easily than a set-in mark, and set-in marks on chrome or wheels have no method beyond the maker's approved cleaner. Pick your approach by the finish, since bare metal, painted metal and chrome don't all handle wiping the same way.
Mildew on a painted aluminum shed and mold inside a metal water bottle rarely call for the same product. For a water bottle, choose something you'd trust around food and rinse it thoroughly afterward. If you're working on mold on stained railings, a finish check comes before any remover.
Before you start
What metal, chrome & tools can take
Safe to use1
- Water
Use with care6
- Hot water
- Soaking
- Chlorine bleach
- Solvents (alcohol, spot removers)
- Acids (vinegar, lemon)
- Scrubbing and abrasives
Avoid1
- Heat, once the stain is out
9 items
What you'll need
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- GlovesKeep spores off your skin. (opens Amazon)
- Goggles without ventsKeep spores out of your eyes. (opens Amazon)
- N-95 respiratorKeeps you from breathing in spores. (opens Amazon)
- Stiff brushKnocks loose mold off outdoors before you wipe. (opens Amazon)
- Mild liquid dish soapMakes the sudsy water, and is the only cleaner for chrome and anodized aluminum. (opens Amazon)
- AmmoniaA few drops in warm water make the wipe for most metal. (opens Amazon)
- ClothApplies the wipe and picks up the mold.
- Clear waterFor rinsing the cleaner off.
- Commercial mildew stain remover (optional)Only for a stain that stays after the wipe. (opens Amazon)
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5 steps
Step by step
Step 1 of 5
Protect yourself before you start
Put on gloves, goggles without vents, and an N-95 respirator before you touch the mold. You want to keep spores out of your lungs and off your skin, so don't skip this even for a small spot.
Step 2 of 5
Stop the moisture source
Find what keeps this metal wet, such as a leak, condensation, or a damp storage spot, and fix it. Mold can't grow without water or moisture, so cleaning alone won't stop it coming back.
Step 3 of 5
Brush off the loose mold
Take the item outside if you can and brush off any loose mold with a stiff brush. Doing this outdoors keeps the spores from scattering through the house.
Step 4 of 5
Wipe with warm ammonia water
Dip a cloth in warm water with a squirt of mild liquid dish soap and a few drops of ammonia added, then wipe the stain thoroughly. Rinse the cloth as it fills with mold so you're not spreading it back onto the metal.
Tip. Work in small sections so the solution doesn't dry on the metal before you wipe it off.
Careful. Strong alkaline cleaners discolor chrome and anodized aluminum, so keep the ammonia to a few drops in warm water, and on those finishes use mild dish soap and water instead.
Step 5 of 5
Rinse and dry completely
Rinse the metal well with clear water and wipe it dry. Let it dry fully before you use or store it, and fix any spots that stay damp.
Careful. Leftover moisture causes rust on steel, so a damp item shouldn't go back into storage.
If you'd rather buy than mix
Best products for mold on metal, chrome & tools
Test the ammonia mix on a hidden spot first, especially on painted or chrome finishes, before you wipe the visible stain.
Amazon Basics Microfiber Cleaning Cloths
How we picked these: each product is made for this type of stain, its maker doesn't warn against using it on metal, chrome & tools, and its directions fit the steps above.
Finished the steps? How does it look?
Nice work. Let it dry completely and check it again in good light. Here is what done looks like:
How to tell it's really gone →A faint mark usually needs one more round, not a stronger product.
Heavy buildup usually takes more than one round.
Heavy or long-standing buildup →When to call a professional →How to tell it's working
The metal should look even and clean once it's fully dry, with no fuzzy patches or dark spots left. Check it in good light from a few angles, because a faint shadow can still show while the surface is damp.
What changes for yours
Adjust for your metal, chrome & tools
Metal or aluminum water bottle
Mold in a bottle usually sits on the inside, where water pools, so empty it and use a bottle brush to reach the walls, the base and the neck. Clean the lid separately, since a cloth won't reach the threads.
Use the same warm sudsy ammonia water, then rinse thoroughly with clear water until no soap is left. Dry the bottle with the lid off so air can reach the inside.
Painted aluminum shed
Start with the ammonia wipe, but test it on a hidden spot first, since ammonia's effect on this paint isn't known. If the paint dulls or lifts, stop and switch to mild dish soap and water.
Work in small sections so the solution doesn't dry on the panel before you wipe it. Check the finished panel in daylight once it's fully dry.
Stained railings
If the railing is metal, the same brush, wipe and rinse steps apply, and you should test first on any painted or coated finish. If it's wood, the cleaning is different, so follow the Decks & Wood Fences guide instead.
Work from the top down so drips don't land on sections you've already cleaned, and rinse the lower rails last.
Heavy or long-standing buildup
If the mold has been there a long time, the first wipe may only lift the top layer. Repeat the warm ammonia wipe once on the same spot before you try anything stronger.
Mold that has dried onto the metal needs another wipe rather than harder scrubbing, because abrasives scratch chrome and cause discoloration on anodized aluminum. If it still shows, test a commercial mildew stain remover on a hidden spot, then apply it per the package directions.
If the mark is still there after the commercial remover, the realistic choice is to live with it or replace the item. Stop before the finish starts to change, since more scrubbing won't undo that.
Vinegar, baking soda, peroxide and more
Do home remedies work on mold on metal, chrome & tools?
Many household mold remedies are wrong for metal, and a few can damage it. Start with warm water and mild soap, and use bleach or solvents only with care.
Works1Skip3Avoid3
What makes it worse
Mistakes to avoid
Don't use bleach on this metal
Bleach is not safe on non-stainless steel, aluminum or silver, and it should never be mixed with ammonia because toxic fumes can form. Bleach is not a routine mold treatment, so there's no reason to reach for it here.
Don't scrub chrome with steel wool
Steel wool and abrasive pads scratch chrome, even on stubborn spots. Use a soft cloth and let the warm wipe and a repeat pass do the work.
Don't paint over mold
Paint applied over mold is likely to peel, so the surface needs to be clean and dry first. Give the metal time to dry completely before you paint it.
Don't clean hot metal
Cleaners shouldn't go on hot chrome or metal, so let the item cool before you start the wipe. Check the metal with your hand first, especially on a railing or shed that's been in the sun.
When to call a professional
If the mold covers more than about 10 square feet, or came from sewage or contaminated water, don't tackle it yourself. Follow published remediation guidance or hire an experienced professional.
Questions
What cleaner kills mold on food-contact steel?
No cleaner approved for killing mold on food-contact steel appears here, so don't guess at one. Wash the item with warm water and mild liquid dish soap, rinse well, and dry it completely. Keep bleach and hydrogen peroxide away from it, since both are ruled out for metal containers.
What is mold, and why does it show up on metal?
Mold is a living fungus, and its spores land on wet surfaces and start to grow there. None of them grow without water or moisture, which is why a stain on metal usually points to a damp spot nearby.
Will mold come back on metal?
It can, if the metal stays damp. Wet areas dried within 24 to 48 hours usually won't grow mold, so dry the item fully and fix whatever keeps it wet.
Can mold spread from one metal item to another?
Spores can scatter when you disturb loose mold indoors, so brush it off outside when you can. Keep the cleaned item away from other items until it's fully dry.
Does mold leave a permanent mark on metal?
It can. Mold may cause staining and cosmetic damage that can't always be reversed, so a faint mark may remain after a thorough clean.
Should I run the heating or cooling system if the metal ducts have mold?
No, not if you suspect the system is contaminated with mold. Running it can spread mold through the building, so have it checked before you use it again.
Mold on other materials
Other stains on metal, chrome & tools
Start from the bigger picture
How we know this
Every method, amount and warning here comes from university extension services, industry bodies and product makers. We read them, check every step for unsafe combinations and changed amounts, and write it up so you can follow it.