Cleaning dirt/mold off aluminum window sill
August 17, 2023 6:52 AM Subscribe
I've tried several things, but this black mold/dirt has baked into my alunimum window sills from decades in the direct sun and will not be budged. Suggest what other cleaners might work?
My screened porch has metal window sills from the 1960s-70s (I'm guessing they're made of aluminum). These have a lot of black/gray spotting that I assume is mold (maybe some dirt too?) baked in by decades broiling in the direct sun.
I've tried standard house cleaning spray, Mr. Clean Magic Eraser, and Bar Keepers Friend. I've tried leaving the cleaning chemicals on for a long time to soak, getting it really saturated, and scrubbing very hard (including using a power drill scrubbing brush attachment). I have not tried bleach yet but am willing, if anyone can recommend a specific brand/product. (I can't get all the storm windows open yet because of rust, so hard to adequately ventilate.)
I don't care if the sill is left damaged/scratched, just don't want it to look like there's mold (so people don't have health concerns/can sit on the porch without worrying about breathing in something bad).
What kind of cleaner would you try next? Thanks!
Photos here!
My screened porch has metal window sills from the 1960s-70s (I'm guessing they're made of aluminum). These have a lot of black/gray spotting that I assume is mold (maybe some dirt too?) baked in by decades broiling in the direct sun.
I've tried standard house cleaning spray, Mr. Clean Magic Eraser, and Bar Keepers Friend. I've tried leaving the cleaning chemicals on for a long time to soak, getting it really saturated, and scrubbing very hard (including using a power drill scrubbing brush attachment). I have not tried bleach yet but am willing, if anyone can recommend a specific brand/product. (I can't get all the storm windows open yet because of rust, so hard to adequately ventilate.)
I don't care if the sill is left damaged/scratched, just don't want it to look like there's mold (so people don't have health concerns/can sit on the porch without worrying about breathing in something bad).
What kind of cleaner would you try next? Thanks!
Photos here!
Best answer: I strongly suspect that's pitting--corrosion--of the alumnium. Basically aluminum rust. It's not mold and is not a health concern.
posted by pullayup at 7:00 AM on August 17, 2023 [11 favorites]
posted by pullayup at 7:00 AM on August 17, 2023 [11 favorites]
Best answer: Yeah, I don't think that's mold. A quick Google search suggests that you can clean aluminum corrosion with a dilute mixture of water and vinegar. There are also products you can buy on Amazon. Note that I don't have any experience with any of this stuff.
posted by alex1965 at 7:14 AM on August 17, 2023
posted by alex1965 at 7:14 AM on August 17, 2023
Best answer: Aluminum corrodes, usually slowly. One of the polishes may help reduce it.
posted by theora55 at 7:41 AM on August 17, 2023
posted by theora55 at 7:41 AM on August 17, 2023
Response by poster: This might not be visible from the photos, but the (mold? dirt? corrosion?) is clearly sitting raised abovethe top of the metal, rather than being flush with/part of the metal itself. (I'm not familiar with corrosion, so it could still be that and the corrosion makes it bump out? But wanted to share in case that rules corrosion out.)
Thanks very much for answers so far!
posted by rollcredits at 9:33 AM on August 17, 2023
Thanks very much for answers so far!
posted by rollcredits at 9:33 AM on August 17, 2023
Best answer: anderjen - top Amazon review of Mold Armor (which I'm thinking, is probably mostly bleach)
"Does Mold Armor work? That is the wrong question, fellow mold fighter. The question is - should you dare to use it at all? It was upon my second use of the concoction that I’d gone too far, sprayed too vigorously, and released a monster that almost claimed my home.
It started with an innocent bathroom cleaning regimen. I was to spray the tiles, and while the fluid did its work, I would clean the remainder of the bathroom.
I sprayed Mold Armor gleefully, high and low, every black spot in my shower got doused in a chemical bath. As advertised, I saw the effects in real-time. The dark clouds of mold parted so quickly that I could almost hear their screams. I chuckled - take that you pests! I resumed using a more tame cleaner on the sink, but in a few minutes, I noticed my nose start to run. Shortly after, my lungs ached and my eyes started to burn. The microbiome and mucous membrane in my body were now under assault. I saw the fading black mold now was a portent to my own fate.
The effect intensified as the oxygen level plummeted. Every orifice leaked from my face as if I were inside a WWI trench filled with mustard gas. I hastily opened a window, but Mother Nature sent no aid - on this day there was no breeze.
The process had begun. The atmosphere in my 140 sq foot bathroom was being converted into a Venus-like atmosphere and there was nothing I could do to stop it. My vision blurred. I bolted out of the bathroom, up the stairs, and into my garden. I grabbed a handful of grass and snorted it like a cocaine addict, but couldn’t smell a thing.
Unfortunately, in my haste, I left my phone behind. I re-entered the transformed atmosphere. Would my phone be reduced to a lump of molten metal and plastic, or evolved into a new lifeform, sentient and pissed off, like an Uruk-hai pulled from Saruman’s mud?
I had to know.
With a wet rag and eyes half closed, I turned on the shower, and the dehumidifier, and then rescued my phone from the window ledge. My lungs still burned, but my phone had resisted both decomposition and evolution, for now. I proceeded to open all the windows in my house, unwilling to cede my home to this ongoing unterraformation. With time, the smell abated. I opened the door.
The bottle of Mold Armor sat proudly on the tub. Behind it, tiles that looked as if they were hewn from the earth yesterday glimmered in the setting sunlight of the summer afternoon.
I picked up the bottle as if I were holding a nuclear reactor core. Was this a Pyrrhic victory? Trading cell degradation in my lung tissue for a clean shower seemed silly, but, man, did it look great!"
posted by bitterkitten at 9:43 AM on August 17, 2023 [6 favorites]
"Does Mold Armor work? That is the wrong question, fellow mold fighter. The question is - should you dare to use it at all? It was upon my second use of the concoction that I’d gone too far, sprayed too vigorously, and released a monster that almost claimed my home.
It started with an innocent bathroom cleaning regimen. I was to spray the tiles, and while the fluid did its work, I would clean the remainder of the bathroom.
I sprayed Mold Armor gleefully, high and low, every black spot in my shower got doused in a chemical bath. As advertised, I saw the effects in real-time. The dark clouds of mold parted so quickly that I could almost hear their screams. I chuckled - take that you pests! I resumed using a more tame cleaner on the sink, but in a few minutes, I noticed my nose start to run. Shortly after, my lungs ached and my eyes started to burn. The microbiome and mucous membrane in my body were now under assault. I saw the fading black mold now was a portent to my own fate.
The effect intensified as the oxygen level plummeted. Every orifice leaked from my face as if I were inside a WWI trench filled with mustard gas. I hastily opened a window, but Mother Nature sent no aid - on this day there was no breeze.
The process had begun. The atmosphere in my 140 sq foot bathroom was being converted into a Venus-like atmosphere and there was nothing I could do to stop it. My vision blurred. I bolted out of the bathroom, up the stairs, and into my garden. I grabbed a handful of grass and snorted it like a cocaine addict, but couldn’t smell a thing.
Unfortunately, in my haste, I left my phone behind. I re-entered the transformed atmosphere. Would my phone be reduced to a lump of molten metal and plastic, or evolved into a new lifeform, sentient and pissed off, like an Uruk-hai pulled from Saruman’s mud?
I had to know.
With a wet rag and eyes half closed, I turned on the shower, and the dehumidifier, and then rescued my phone from the window ledge. My lungs still burned, but my phone had resisted both decomposition and evolution, for now. I proceeded to open all the windows in my house, unwilling to cede my home to this ongoing unterraformation. With time, the smell abated. I opened the door.
The bottle of Mold Armor sat proudly on the tub. Behind it, tiles that looked as if they were hewn from the earth yesterday glimmered in the setting sunlight of the summer afternoon.
I picked up the bottle as if I were holding a nuclear reactor core. Was this a Pyrrhic victory? Trading cell degradation in my lung tissue for a clean shower seemed silly, but, man, did it look great!"
posted by bitterkitten at 9:43 AM on August 17, 2023 [6 favorites]
Best answer: This might not be visible from the photos, but the (mold? dirt? corrosion?) is clearly sitting raised abovethe top of the metal, rather than being flush with/part of the metal itself.
That's prrrrrobably aluminum hydroxide, Al(OH)3. Here's a simplified schematic illustration of the pitting reaction. This is pretty similar to how rust (ferric/iron oxide, Fe2O3) can be rough or raised above the surface of the uncorroded iron or steel.
posted by pullayup at 11:07 AM on August 17, 2023 [1 favorite]
That's prrrrrobably aluminum hydroxide, Al(OH)3. Here's a simplified schematic illustration of the pitting reaction. This is pretty similar to how rust (ferric/iron oxide, Fe2O3) can be rough or raised above the surface of the uncorroded iron or steel.
posted by pullayup at 11:07 AM on August 17, 2023 [1 favorite]
Best answer: Steam cleaners are pretty good for built-up gunk.
posted by dum spiro spero at 11:12 AM on August 17, 2023
posted by dum spiro spero at 11:12 AM on August 17, 2023
Best answer: It looks like oxidation to me. Aluminum takes some cleaning and prep prior to welding, and here's what I do, from least to most aggressive.
1.) If it's relatively clean, wiping it down with acetone works well. (Note: acetone eats nitrile gloves)
2.) Next step would be a white vinegar solution. 2-3Tbsp of white vinegar to 4 cups of water, mix and boil for 10-15 minutes. Cool, and use this mild acid solution to clean the parts. A plastic-bristle scrubber brush may help. This will clean the area, but you still may have a rough, pitted surface left behind; polishing may help some.
3.) Next option would be a wire brush. Stainless steel bristles, preferably a brush you'll use only for aluminum, because small bits of aluminum will gall up the brush, which can contaminate steel parts. You can also use steel wool, but again, reserve this brush or wool only for use on aluminum, so you don't contaminate other parts. Both a brush and steel wool will leave fine scratches in the surface, so be aware of that, if that's an issue. A "toothbrush" style hand-held brush should work fine, but if you choose to use something powered, like a wire wheel or a wire cup in an angle grinder or a drill or a dremel, please be aware that a wire wheel loves to grab the edges of things and either yank the tool or the part around, and wire "whiskers" will definitely fly off the wheel in use, so proper eye protection and good cleanup afterwards are a must. The brushes I linked do not last long and are disposable, but they are super handy for general scrubbing around the shop.
Whatever path you take, whatever cleaners you use, give it a good final wipe with acetone to clean up any remaining cleaners, for good measure. Don't want to leave anything too aggressive on the metal, possibly corroding it further.
posted by xedrik at 12:21 PM on August 17, 2023 [3 favorites]
1.) If it's relatively clean, wiping it down with acetone works well. (Note: acetone eats nitrile gloves)
2.) Next step would be a white vinegar solution. 2-3Tbsp of white vinegar to 4 cups of water, mix and boil for 10-15 minutes. Cool, and use this mild acid solution to clean the parts. A plastic-bristle scrubber brush may help. This will clean the area, but you still may have a rough, pitted surface left behind; polishing may help some.
3.) Next option would be a wire brush. Stainless steel bristles, preferably a brush you'll use only for aluminum, because small bits of aluminum will gall up the brush, which can contaminate steel parts. You can also use steel wool, but again, reserve this brush or wool only for use on aluminum, so you don't contaminate other parts. Both a brush and steel wool will leave fine scratches in the surface, so be aware of that, if that's an issue. A "toothbrush" style hand-held brush should work fine, but if you choose to use something powered, like a wire wheel or a wire cup in an angle grinder or a drill or a dremel, please be aware that a wire wheel loves to grab the edges of things and either yank the tool or the part around, and wire "whiskers" will definitely fly off the wheel in use, so proper eye protection and good cleanup afterwards are a must. The brushes I linked do not last long and are disposable, but they are super handy for general scrubbing around the shop.
Whatever path you take, whatever cleaners you use, give it a good final wipe with acetone to clean up any remaining cleaners, for good measure. Don't want to leave anything too aggressive on the metal, possibly corroding it further.
posted by xedrik at 12:21 PM on August 17, 2023 [3 favorites]
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posted by anderjen at 6:59 AM on August 17, 2023 [1 favorite]