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Aluminum shiny finish destroyed in dishwasher

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Q. I recently placed a new shinny aluminum meat-mallet (tenderizer) in our dishwasher. It came out almost black and looks terrible. Can I do anything to restore the original finish or at least a clean looking finish. What would have caused this? Was it anodized or something? Could anodizing be removed simply by washing in a dishwasher. Was there a chemical reaction or dissimilar metal issue?

Any advice appreciated as my wife wants to kill me for damaging it. She may even use the meat tenderizer to do it! I would at least like to be killed with a clean, shiny object

Gary Cay
Plastics - Sydney, Australia


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A. Metal polish; most likely you managed to oxidize the surface of the metal. Just use whatever metal polish you have handy to remove the surface oxidization, if you don't have any, try toothpaste.

Marc Banks
Blacksmith - Shawboro, North Carolina


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thumbsup2Take the easy way out. Sneak out and buy an identical one. Rub it a tiny bit with toothpaste, give it to the lovely lady and tell her that you "polished it" No lie, but not the whole truth either.

P.S., keep this one in the hand wash category.

James Watts
- Navarre, Florida

misc. plating stuff
For Sale cheap



February 15, 2011

A. Try making a paste of water and cream of tartar (available in the spice aisle at the grocery store, if not already in your kitchen cabinet). Use either a clean cotton cloth, or in this case, an old tooth brush, nail brush or sponge, and work the paste until the shine has been restored.

Kim Pace
- Fort Worth, Texas

wikipedia
Cream of Tartar



Dishwasher caused white spots on aluminum cake pans

May 16, 2010

Q. I ran my 9 inch round aluminum cake pans through the dishwasher and they have a few white powdery spots on them. My questions are:
1) what are these white spots and what causes them?
2) does this mean that my pans should be tossed out? (they are pretty old - they belonged to my grandmother who was born in 1908.)
3) should I avoid putting these and other aluminum baking pans in the dishwasher?
Thank you

Marjorie Moats
bake for fun when I can - Cleveland, Ohio, USA

First of four simultaneous responses -- May 19, 2010

A. Dishwashing detergent is quite hard on aluminum pans that have not been anodized. They have an oxide layer that allows the pan not to corrode. Clean with a plastic sponge scrubber in warm water, coat the pan with a Light coat of oil and bake at 350 °F for an hour or so. Let it cool down in the oven. Should work fine.

James Watts
- Navarre, Florida

Second of four simultaneous responses -- May 19, 2010

A. Marjorie,
Aluminum is sensitive to harsh detergents. Most dishwasher detergents are alkaline in nature. The good news is, the white spots can be removed. Buy a small jar of cream of tartar in the spice section of the supermarket. Mix in a small amount of warm water to form a paste. With a medium coarse rag rub the paste over the whole pan in a circular motion giving added time to the white spots. Rinse well with warm water and towel dry. You may have to repeat the process. I would use a mild dish detergent and wash pans by hand from now on.

Mark Baker
process engineer - Malone, New York


Third of four simultaneous responses -- May 19, 2010

A. Hi Marjorie,

This sounds like the aluminum was oxidized during the wash phase. Are you even supposed to put aluminum in a dishwasher?

Okay, so here's what's happening:

Your dish-washing detergent contains alkaline phosphates. At high pH, the 'passive' aluminum surface dissolves as Na2Al(OH)4 (sodium aluminate). This reveals 'active' metal underneath, which reacts with the phosphates in the water to form aluminum phosphate. Sodium aluminate reacts with sodium phosphate to form sodium aluminum phosphate. Sodium aluminum phosphates precipitate out of the water, and deposit onto the sites along the surface of the aluminum cookware, leaving these powdery spots.

Sodium aluminum phosphate isn't dangerous if you accidentally consume. It's often used as a leavening agent for baking. If you scrub the surface with a Brillo pad, this should be fine to use again.

In the future, try to clean baking sheets by hand; dishwashers provide a corrosive environment for aluminum.

Robert Kinner
- Toledo, Ohio


Fourth of four simultaneous responses -- May 20, 2010

A. The aluminium that the cake tins are made from is probably being attacked by the dishwasher powder. This is starting to cause corrosion which is the white spots. My advice would be to clean the tins with some of the more abrasive pan scourers to remove the corrosion, rinse well. Put a light coating of vegetable oil on the pans with kitchen roll before putting them back into your cupboard. From now on only hand wash them.

Ciaron Murphy
- South Wales UK



Aluminum meat grinder parts washed in dishwasher turned gray

November 4, 2010

Q. A friend borrowed our meat grinder and washed the aluminum parts that are not dishwasher safe in the dishwasher! The once pretty shiny silver looking parts are now dark gray and leave a black tarnish on your fingers. How can I clean it, to get it to the point where it will be safe to use again?

Tawny Dunlevy
Homemaker - Sitka, Alaska, USA

November 4, 2010

A. Hi, Tawny

I think it's safe to use, and I believe if you look it up in authoritative places you will find the same opinion expressed by the Alzheimer's Association, EPA, etc. But that black smut is unappealing and if you can get rid of it temporarily, consider yourself lucky.

I used your inquiry as a teachable moment for myself, taking an old aluminum ice cream scooper that has been in the dishwasher a hundred times and seeing what I could do with it. Rubbing it with a cloth soaked in vinegar took off loads of the black smut, but was generating it almost as fast as it took it off :-) After I rinsed it, not much further black smut came off, and it was darker in color because I had dissolved any white corrosion products. I then tried a sulfamic acid metal polish and the experiment went pretty much the same. Not having any Mother's Mag & Aluminum Polishamazoninfo at hand, I tried rubbing compound (by hand), and the result was slightly better.

Moving on to conjecture, I think you could brighten it up and remove the black smut if you buff it with a power tool (a buffer, a Dremelamazoninfo, or at least a buffing pad on a battery operated drill) and the Mother's. But I think once the anodized coating is gone, it's gone, and it will not stay shiny for long. Sorry.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey

P.S.: We merged several separate threads together here to consolidate the information, so it's not that readers are blowing off the other postings ... they weren't there. For example, I'm not suggesting that cream of tartar won't work; rather, that was a suggestion that actually came after my posting. Sorry for the confusion.


November 9, 2010

A. It has been a while since I've read through it, and I don't have my copy handy, but I recall Wernick Pinner and Sheasby =>
stating that you could get really good corrosion resistance by submerging aluminum in boiling water for 24 hours but that it wasn't economical for most manufacturing purposes. In this case however, if you CAN brighten it back up (even temporarily), if you have a way to boil it for long enough it MIGHT stay that way. Mind you, I've never personally tried it.

Good Luck!

Jim Gorsich
Accurate Anodizing Inc.

Compton, California, USA


Wernick, Pinner & Sheasby
Surface Treatment & Finishing of Aluminium and Its Alloys


November 2013

thumbsup2Great idea, Jim, thanks.

Readers: Sorry I couldn't easily find exactly what Jim was talking about (no surprise though, the book is almost 1300 pages). But I did see graphs showing that the oxide film does continue to grow for 16 to 24 hours in boiling water before it tops out. Some other pages seem to indicate that deionized/distilled water is very important, so try boiling in a very clean enameled pot (or a pot lined with a pot liner or at least a plastic bag), and maybe change out the deionized/distilled water a couple of times.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey


December 8, 2010appended

Q. I washed my aluminum pressure cooker in the dishwasher. The manual says not dishwasher safe on it; however, I did not see that until later. Instead of being shiny silver it is now dull and has a pink/purple/green tinge to it. Is this safe to use again or should I discard it?

Cat Welz
- Vernon, Connecticut, USA


December 9, 2010

Hi, Cat.

I'd guess that the pink/purple/green tinge is a diffraction pattern caused by the very thin last of the anodized coating (sometimes you see automobile headlights shifting color as they approach you if they have anodized reflectors). With a ruined pot, this sounds like the perfect try to try Jim's proposed cure of boiling distilled water in it for 24 hours. Please let us know what happens!

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Brick, New Jersey


January 26, 2013

A. There IS hope for dishwasher discolored aluminum items. My beautiful Arthur Court Measuring spoons were accidentally washed in the dishwasher. I researched on-line and decided the "least likely to do more damage" approach would be the Brillo Pad solution. IT WORKED! I rubbed & scrubbed with a blue filled pad until they were covered in blue goo. This is going to take serious rubbing! Then I used a soft bristle brush & warm soapy water to briskly brush them repeatedly to remove all tarnish and blue goo. I used a little more dish detergent & clean warm water to brush them again and rinsed in warm water. Then I dried them with a soft clean towel. Never underestimate a Brillo Pad & elbow grease! Amazing! I am submitting photos.

Arthur Court measuring spoons 1 Arthur Court measuring spoons 2 Arthur Court measuring spoons 3
Arthur Court measuring spoons 4 Arthur Court measuring spoons 4

Amber Miller
- Iowa City, Iowa


November 24, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. Hello. I have 2 vintage aluminum (I believe cast) decorative bowls, on of which is a Royal Hickman RH7 Signed Bruce Fox Aluminum Leaf Tray. After a party, my husband put them in the dishwasher and they now have lost their luster and there are darker streaks and spots. Is there a way to restore them?

Karen Caldwell
- Sonora, California
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