Anodizing 6061 Or 6063 Al For Maximun Abrasion Resistance 2

[norumba]

Hi everyone,

Some extensive (and sometimes conflciting) research on the net has led me to this forum, where I've been reading and digesting more info over the past day or so. I'm hoping I can prevail on some of the expertise here (kenvlach still around?).

I found the thread342-137386, thread404-66479, and thread338-138745 threads very illuminating, and hope i can ask some follow up issues here.

I'm needing about 4 or 5 strips of aluminum sheet either 6061 or 6063, for use as a fingerboard for a fretless electric guitar.

Preliminary dimensions are 0.250" thick by 2.5" wide by 22" long. There will also need to be applied a radius of about 20" across the width (not the length) of the strip. This is a rough cut dimension, as the guitar builder will machine it down to the precise dimensions, including the radius.

The piece must be able to withstand the near constant abrasion from the strings, more so that a regular fingerboard (this is for an east Indian style of music, utilizing a lot of precise, often fast constant lengthwise sliding from, between, and to the notes). So wear and abrasion resistance are very important factors for this piece.

At the same time, the surface has to feel very light, fast, and smooth, not sticky, with as low a coefficient of friction or drag as possible. Yet I think too much of a teflon coating type approach would overly dampen tone.

Surface also needs to be somewhat heat resistant -- current brass fingerboard expands slightly under heat, either from friction-induced heat from fast playing of sliding notes or from lighting conditions. The heat has two consequences, one of expanding the metal so that strings are choked off (the tolerance for string height tolerance is much lower than on a conventional guitar, about one sheet of paper thickness), and the other symptom is of increased drag and resistance. Perhaps the heat effect is to the sealant /finish, but that instrument is from a commercial builder who understandably keeps his process and specs proprietary, so I'm not sure.

Some thought should also be given to corrosion resistance - while this isnt played underwater, lol, there is the aspect of skin and perspiration chemistry.

While developing the idea, I thought aesthetically it would be nice to have the fingerboard anodized to a nice rich burgundy or maroon, but I'm open to other colors (black, medium or dark bronze).

Some questions:

1) I'm getting conflicting research re alloys. Some initial sources said that 6061 doesn't anodize well, though more detailed research here and elsewhere obviously shows it can be done. i was looking at 6063, but builder wants pretty good rigidity and stiffness, but we need a pretty smooth surface as well. Reconsidering 6061, based on info gleaned here.

What alloys /temper would others recommend, and when purchasing from a metal supplier, what treatment should it undergo - cold or heat treated, annealed? With the anodizing options to be considered, and the aspects of stiffness and rigidity, etc, I need to be specific to my supplier, and I'm not experienced enough to know what to ask for.

2) Preliminary research seems to point to a hardcoat anodize process; however, others made the point in thread404-66479 that there is a decrease in abrasion wear and hardness with increasing thickness (see kenvlach's posts on that thread). Research on that thread and elsewhere, balancing all of the factors, still seem to indicate a hard anodize with mid temp dichromate seal, with perhaps some kind of epoxy and PU topcoat. I'd love to know if I'm on the right track, or if there's another approach I haven't found yet, considering the parameters outlined above. I'm open to options.

3 ) Keeping in mind those parameters, can someone offer any specific epoxies and PUS to recommend and any application methods that my builder wouldn't already know about (sander/buffer/polisher he is, but mainly with woods - anything unique to working with the anodize?)

4) what kind of coloring options do I have, taking all of the above into account?

5)Finally, the back surface will be bonded to a wooden neck. we want as little absorption of energy or give as possible. I looked at this adhesion thread -thread16-40718 - but am unsure if any of that would change with the wooden factor. best way to finish or seal that back side of the Al piece?

Many, many thanks in advance for your time and input.

 

[MintJulep]

For the playing surface, a Teflon-impregnated hard coat anodize seems to meet your requirements. I know you had your doubts about "Teflon coating", but with the impregnated finish, the Teflon is in the surface layer, not on it. If you want to touch an example, go to the pots and pans section of a store and look at the high-end pans like Calphalon or Analon - they use Teflon-impregnated hard coat anodize - as opposed to the lower-end Teflon coated pans.

I've never see it in any color other than black.

As for bonding it to a wood neck: I would be worried about shear stress as the wood expands and contracts with changes in moisture. To counter that, you would typically want a relatively thick layer of adhesive so that the shear has some distance to work over.

I would be tempted to experiment with a good epoxy, and maybe even add a layer of 8 or 10 oz glass between the wood and the aluminum to serve as a spacer and prevent the epoxy from being squeezed out by over-enthusiastic clamping.

Obviously, if you are bonding the back side, you don't want that finished with the Teflon. Clean clean clean is the rule.

 

[norumba]

hi MintJulep,
many thanks for your response!... ill go looking at those high end pots, definitely. while im not opposed to that approach, I think I need to research any possible tonal implications. The neck contributes a surprising amount of tonal quality to a guitar, so how Teflon would affect overtones, string energy absorption, etc, all have to be analysed. Worth investigating...

The idea in general does make me also think of something like a dry film lubricant approach (graphite, fluorocarbon, etc), so I'll start looking into that as well.

one thing i forgot to mention in the previous post - some of the playing technique involves contacting the string with the edge of the fingernail itself, rather than th e fingertip pad, so thats another reason form maximum abrasion resistance.

as to adhesion, hose are good and interesting points - i think the builder has the moisture element under control via choice and treatment of neck wood, truss rods, etc. ill pass on your points to him for sure, though as it as a factor in the mix.

thanks for responding -- looking forward to all thoughts!
happy 4th everyone!

 

[unclesyd]

Look on the bottom of this page at Hardtuf process for Al.

http://www.tiodize.com/anodizing.html

 

[norumba]

thank you unclesyd, thats a very helpful link.... seems quite promising. still wondering what the sound is like and whether any further eopxy or PU topcoating is necessary. ill email them...

 

[unclesyd]

We ran it as is though our synthetic fiber probably imparted as coating which would have been mainly a wax.
An Email is OK, but if you can get a contact a phone call usually works a lot better

 

[TVP]

norumba,

I would be concerned that the aluminum oxide coating will damage the strings. The hardness of aluminum oxide is > 2000 HV while that of a guitar string is probably ~ 500-700 HV. A PTFE-impregnated anodized layer would be better than just the anodized layer by itself. Have you considered a different base material like bronze or steel with a low-friction coating?

 

[norumba]

hi TVP,
i dont have HV numbers for the strings, but strings come in different alloys -- usually either some kind of nickel alloy or sometimes stainless steel. I don't use the steel ones for the very reason you mention, but nickel doesnt seem to be a problem.

I'm open to other metals - the sarod , a traditional instrument I also play, has a fretless plate of steel, but all the strings are unwound and playing style is a bit different than the guitar.

the main reasons for considering aluminum was primarily the weight factor and also its acoustic properties - there are a some regular fretted electric guitars machined entirely from aluminum! If aluminum works, it may even be a better choice as a neck plate for the traditional sarod, but again, I'm open to options.

 

[norumba]

i checked out the Calphalon pans --- the hard coat anodize exteriors on the professional line felt pretty good, but the nonstick interior cooking surfaces felt a little grainy...

 

[MintJulep]

The graininess is largely a function of surface finish before anodizing. I've had some super smooth and flat surfaces Teflon-hard coated and they come out super smooth.

The exteriors are just hard-coat anodize, I think.