I've recently completed a few parts and was wondering why my 6061 series aluminum parts scratch so easy.

Do I need to have them anodized, sealed, or power coated to prevent this?




I've also tried holding a steel wool dishwashing pad for a polish surface (second picture), but it's not really coming out the way I want it.


Any help would be greatly appreciated.

Do I need to have them anodized, sealed, or power coated to prevent this?



Yes

Anodizing is the best. It will give you a moderately scratch resistant surface that can be colored. Also anodizing does not change dimensions by very much, normally less than 0.0005" whereas powder coating adds a layer of plastic coating anywhere from .005" to 0.020" thick which can chip off.

What kind of finish where you trying to get with steel wool? All it will do is give you a very unevenly scratched surface.

"What kind of finish where you trying to get with steel wool? All it will do is give you a very unevenly scratched surface."


A brushed look. I read that another individual use this method and decided to try it. I guess it didn't work to well. Any other methods to get this look?



You know I was thinking of getting it burnished, kind of like how they use to polish silverware, but I'm thinking that this might leave a pretty bad finish.

Try experimenting with the different grades of Scothbrite; some can give reasonable looking surfaces just by hand rubbing. Also experiment with different lubricants including different types of soap and detergent.

Back in the days when I did prototypes and one-offs I played around quite a bit hand finishing to get something looking nice off rather crummy manual equipment; now we rarely do anything to the surface directly off the CNC's.

One thing I did work out was a method of hand polishing aluminum with 600 grit wet and dry paper, auto bodyshop stuff, using dish soap as a lubricant and then polishing with Brasso and a linen cloth to get a mirror finish. The same approach also worked with acrylic and I still have a four inch dia. globe and some big prisms I made on a mill and hand polished close to perfectly clear.

Is there any safe DIY way of anodizing the parts black/sealing, without acid/chemicals eating my hand off?

Here's a site that scared the hell out of me, this is what I don't want.


http://gregers.republika.pl/english.html

Is there any safe DIY way of anodizing the parts black/sealing, without acid/chemicals eating my hand off?



'home' anodizing just uses dilute sulfuric acid. You won't accidentally chew your hand off. You can burn yourself, yes, but it would take effort and willful prolonged stupidity. I feel alot safer around sulfuric acid used as an anodizing/plating electrolyte than I do around the average table saw. The sulfuric acid can only do damage in slow motion. Keep some baking soda handy to neutralize accidental splashes or spills. The worst risk is to your clothes, not your health.

(edit: I've done plating and anodizing in my basement shop. My biggest worry? The EPA! They classify any material that touches a plating bath as hazardous waste whether it is or not. This is the reason I don't do home plating anymore; even the relatively harmless Caswell stuff that's about as dangerous as laundry detergent is by my reckoning nudge-nudge-wink-winking at the law. Not all the Caswell stuff is harmless of course, but alot of it is.

Plenty of plating/anodizing techniques do use incredibly nasty, corrosive, dangerous chemicals. There's no reason to use any of those techniques unless you're a commercial operation trying to squeeze the most results out of the lowest operating costs over huge volume. It takes a lot of effort ot be safe with some of that stuff and I can't imagine even a serious hobbyist having the infrastructure for real safety. But you can go a long long way on nothing but dilute sulfuric acid, distilled water, various salts and the occasional solution of lye)

If you're really risk averse, home powdercoating is even safer. ...and I disagree about powdercoating being less durable than anodizing. It depends on the kind of abuse the part is going to get. An anodized surface is much harder, but also *much* thinner. Powdercoating is a plastic layer that will be easier to scratch but harder to penetrate because it's both thicker and flexible. I've not found modern powdercoat to chip (at least not the TGIC or polyester powders, maybe epoxy is different).

Monty