Caring for aluminum.

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Hello and thanks to everyone who responds.  I recently found this forum and am pleased with the wealth of knowledge available to me.  My question is for the treatment of aluminum after being etched or ground down.  I see modern wall art pieces the people say are "pure metal" and "hand ground" to get different textures and light reflections.  I want to take aluminum sheet and make a large piece of wall art that is ground and sanded to make a unique look.  My main question is can you grind and sand bare aluminum and leave it be??  I know aluminum oxidizes and usually gets dull.  So is there a special kind of aluminum needed to do this and keep a bright and shiny finish, or do I have to clear coat over the aluminum after the process is finished to keep it looking sharp?  I have only worked with steel, so I appreciate any knowledge you may provide me here regarding aluminum.
Reply:Back in the early 60's I had just graduated from the Army's Welding School in Aberdeen Proving Ground, MD.  Assigned to the 11th Ordnace Co in Ft Devens, MA.  My weld shop there received a new (and new to the Army) Airco MIGET spool gun.  It was the military version (beefed up drive roller motor and heavier contactor) for welding aluminum armor plate.  Since I was the only welder who had training on the machine, I was elected to set it up, get it opertional, and train the other welders.  I took a piece of 3/8" aluminum plate, and ran a bunch of beads.  I taught the other welders how to weld MIG string beads and weave beads.  By the time we filled the plate with beads, most had the ability to now operate the MIGET.I threw the plate in the scrap metal pile.  A Reservist on his 6 month stint of active duty saw the plate, took it home to Connecticut, cleaned it up and flattened it, sprayed it with clear lacquer, had it framed, and it hangs in his parents home.  When he told me about it, I asked why he did it?  His response "It's a one of a kind piece of art".Anyway, he used clear lacquer coating to prevent oxidation after cleaning.  There are probably other coatings out there to do the same thing.  Good Luck with your project.
Reply:Finishing Aluminum1-Clear coating is not necessary.2-I've had aluminum fuel tanks, outside exposed drive-thru counters--look goodfrom just 'rough' finishing for over 13 years and counting, without any corrosion.The finishing stays looking bright.http://weldingweb.com/attachment.php...1&d=1224435088Basics:-use AL that has no corrosion, if it does, sand that out--first-before any sanding, clean thoroughly, finish by towel wiping with lacquer thinner,two wipe downs are better than one-experiment with sanding, polishing abrasives to get the effect you wish-Carborundum quick-locking, 3M fibratex pads (blue circle) do a great rough finish job--as shown on this AL tank. They have finer grit pads than this rough pad for better finishing. http://weldingweb.com/attachment.php...1&d=1224435125 Attached ImagesBlackbird
Reply:Originally Posted by dave powelsonFinishing Aluminum1-Clear coating is not necessary.2-I've had aluminum fuel tanks, outside exposed drive-thru counters--look goodfrom just 'rough' finishing for over 13 years and counting, without any corrosion.The finishing stays looking bright.http://weldingweb.com/attachment.php...1&d=1224435088Basics:-use AL that has no corrosion, if it does, sand that out--first-before any sanding, clean thoroughly, finish by towel wiping with lacquer thinner,two wipe downs are better than one-experiment with sanding, polishing abrasives to get the effect you wish-Carborundum quick-locking, 3M fibratex pads (blue circle) do a great rough finish job--as shown on this AL tank. They have finer grit pads than this rough pad for better finishing. http://weldingweb.com/attachment.php...1&d=1224435125
Reply:Originally Posted by drewdaddy7Does that tank still look as good today as it does in the picture?  So you are saying with proper preparation and cleaning that the aluminum will not have oxidation after it is ground and exposed to air?  Also does it matter what type aluminum sheet is used? I am sure some are better than others for a project of this type.
Reply:.......obviously it will have 'some'--but apparently, if one changes the polishing media out--as it gets loaded--there's just a very fine layer of oxidation that forms (very quickly--like in minutes)that then protects the aluminum from further oxidation. The 3m pads seem to do a marvelous, fast job at this.So just to get the steps right, you are saying to take the aluminum and clean with thinner.  Sand and get the desired look I am trying to achieve, then polish with some sort of aluminum polish, then a small layer of oxidation will form and protect it from there on out?  Sorry for the questions, this is my first aluminum project.  Also do you suggest any form of treatment in the future to help keep it lasting a long time.  I know you said you have some still looking good for 13 years but I am sure they could always look better as well. Thanks!
Reply:So just to get the steps right, you are saying to take the aluminum and clean with thinner. .....for starters clean off with soap or simple green solution, then lacquer thinner. Sand and get the desired look I am trying to achieve, then polish with some sort of aluminum polish, then a small layer of oxidation will form and protect it from there on out?  .....the molecular thick oxidation I think, actually forms in seconds. --do the sanding, etc. on clean cardboard or other clean surface. Wipe and blow off swarfas it occurs. Change out sand and polishing pads before they get really loaded.If you're trying to get a mirror-like finish, that means progressively finer grit sanding and polishing, then finishing by buffing---that's a whole lot more work and a science in itself. What I've shown is a relatively quick way to make the AL look good and stay that way. Sorry for the questions, this is my first aluminum project.          ....you will need to experiment with abrasives, yourself, to create the visual effects that you wish.Also do you suggest any form of treatment in the future to help keep it lasting a long time.  No. This is not required. Subsequent 'maintenance' polishing can create effects that do not look good.I know you said you have some still looking good for 13 years but I am sure they could always look better as well. Thanks!  ???.....'I say I still have some looking good for 13 years'.....this isn't just my BS--look at exposedaluminum that has been polished on vehicles, boats, aircraft, appliances, etc. I can take and post pics of the coffee kiosk counters, for whatever that's worth. The highly reflective bellies on jet liners are AlClad. Pure aluminum deposited over alloyed aluminum sheet.      Last edited by dave powelson; 10-19-2008 at 02:23 PM.Reason: clarificationBlackbird
Reply:[Also does it matter what type aluminum sheet is used?.....I'd say no. 6000 or 5000 series, I've used them both. I am sure some are better than others for a project of this type......You'll be using either 6000 or 5000 series---more likely 6000 series if sheet or plate. No discernible difference. The indoor use is very light duty.[COLOR="Blue"] I also see a 3000 series on a website that I am looking at prices and thickness of the aluminum sheet.  What are your thoughts on that for what I am trying to accomplish? What is the difference in the three series of aluminum?
Reply:a lot depends on the humidity and temperature. for example in that picture the aluminum is bolted to steel.  If that was in the Pacific Northwest a year outside and the aluminum would have white powder near all the steel connections.  In a dry area like desert the aluminum would show no corrosion.  Clear coats are advisable if it is in harsh environments.  The proper urethane based clear coats with proper filters for sunlight are expensive.  Pure aluminum dead soft has superior corrosion resistance but is weak and not a common choice.
Reply:Also, be careful using an alkali-type cleaner (Greased Lightning, Simple Green, etc) as it will slowly etch and dissolve the aluminum.  Wash, rinse well, and dry should usually be no problem.  Leaving a chunk (or other piece) of aluminum soaking in an alkali will etch/frost/dissolve most aluminum after a while (depending on pH, temperature, dilution of the solution, etc, etc).  The best laid schemes ... Gang oft agley ...