Anodizing sandblasted aluminum?

[rigo430]

Does anyone have any experience anodizing aluminum that has been sandblasted? I've been making parts at work that we used to be able to get nice clean tubing and as of lately we haven't been able to get the material that's in a good condition. Currently I have to sand all the bad spots and then take a scotch bright pad to it to get a decent finish after anodizing. Iwas wondering if i couldjust simply stick it in the sandblaster and get a nice finish after anodizing. They get anodized black which tends to make the defects catch light just right to make all the deffects pop out.

[NC Cams]

Anodizing is the artificicial creation of aluminum oxide on/at the sturface of the part. Hence, you are at the mercy of the surface condition of the part when it comes to cosmetics.

A peened surface should remain about the same and perhaps get a bit rougher depeding on whether or not your anodizing "bites" into the surface or not. Again, since you are chemially changing the surface via a process that changes the surface metallurgy, you are stuck with working with what you have to work with.

You'll probably find that some test pieces, run with varous types of prep, will answer more questions than you'll even propose.

[Geof]

It works perfectly well. The only really critical thing with anodizing is a clean surface totally oil free. With sandblasting you will get a duller looking surface than with scotchbrite. One thing you might find is that after anodizing the finish gets marked more easily when it rubs against something. The anodized surface is very hard, powdered aluminum oxide is an abrasive, but the aluminum underneath is still soft. With sand blasting you have created little peaks and after anodising these are brittle and can rub off. The result is you can get grayish looking areas after use.

[rigo430]

Thanks for the info. The next batch we send of the parts i'll try sandblasting one and see how it turns out if there are any problems with a more of a greying effect i can always scotchbight the surface after using the sandblaster to get out any deeper scratches.

[zenbot]

anodizing a glass-beaded surface gives a really nice satin finish. not as dull as blasting with sand.

[destroyer125]

From my experience as working around anodizing for the past couple years is sandblasting is something to stay away from when anodizing. Glass Bead blasting...Peening....gives you the results you need. Sand particles shatter and stick into the aluminum surface and can disrupt the durability of the coating, and also colored parts will come out akward and greyish in color, some will not take dye at all.

[Pres]

Yep, that's been my experience also with sand vs glass bead.

The glass bead gave a bright satin smooth appearance.
Not as shiney as a freshly machined anodized surface does but it still looks great.

hth,
Pres

[CoatingsGuy]

Sandblasting with aluminum oxide is the best method of texturing the aluminum surface prior to anodizing. Ceramic media also does an excellent job. Glass beads work, however if the separator is not working well, small particles of glass will be imbedded in the aluminum. In all cases, blasting techniques will have very advese visual effects if it is not well controlled and evenly applied. NEVER use media on aluminum that has previously blasted steel, copper, brass, zinc or any other material besides aluminum prior to anodize. You will be very unhappy with the results.

[machinecrafter]

yeah, I agree with you that using aluminum oxide us a good method to texture before anodizing. I use aluminum oxide for a lot of other things to like sandblasting glass, so its always good to have in my shop. I have not tried ceramic media yet but may give it a try. The only blasting material I have is aluminum oxide at the present.

Sandblasting with aluminum oxide is the best method of texturing the aluminum surface prior to anodizing. Ceramic media also does an excellent job. Glass beads work, however if the separator is not working well, small particles of glass will be imbedded in the aluminum. In all cases, blasting techniques will have very advese visual effects if it is not well controlled and evenly applied. NEVER use media on aluminum that has previously blasted steel, copper, brass, zinc or any other material besides aluminum prior to anodize. You will be very unhappy with the results.