Part performance after anodizing

[jlewinsk]

Hi guys! Long time lurker, first time poster.

I've been using Caswell's plating and powder coating system(s) for some time now but I am a complete noob when it comes to anodizing, at least on a personal level. As an Engineering Designer, I've specified anodized finishes of different types for many years. Now I'm working on a personal project out in the garage which involves my car and I'm trying to decide if I should invest in an anodizing system or just farm out the work.

One of the things I want to do is to change the color(s) of all the AN fittings on my hoses. You know the type, Aeroquip or Russel, one piece fittings are usually blue in color, and 2-piece fittings are usually red & blue.

Anyway, I know that the process of anodizing adds a crystalline surface to the part which makes the part "larger" (grow) by ~.001 - .002 per side (the holes would get smaller respectively). The dying process only adds color not thickness, correct? Therefore, if you remove the color by stripping, the part would retain its larger size, correct? If you were to re-anodize the part with a new color, would you be adding a new crystalline surface on top of the old, making the part "grow" even larger?

Now for the kicker. What effect does all of this electrochemical processing have on the structural stability of the original anodized part? In other words, will my fittings still be able to handle the temperatures and pressures of their original design intent?

[acidrain]

You will actually loose material in the stripping/re-ano process. My observations are you will loose .001in per surface. A .5 hole will become a .502 hole after strip and re-ano.
This loss of material is caused by two things... the old ano layer "grew" not only outward, but inward as well. Removing the inward grown material, and a bit of aluminum lost during stripping removes quite a bit of material.
Add the new layer (partially grown inward as well as outward), and get you'll get a net loss of ~.001in. These observations are for type II only... type III would be even more (not your parts).
Long story short... your threaded parts will be just fine stripped and re-ano'd.
If you have an approriate power source and chemicals, you could do your own, but it's fairley inexpensive to have parts re-done for you.
The structural integrity should be fine after re-ano.

[PBInferno]

I've never actually done any of these parts, but I've seen cars with them re-anodized, which means it'll work fine. If you're only going to be doing a few fittings, then it would make more sense cost wise to send the parts out. If you think you'll be doing more anodizing work in the future, you might as well just spend the money on the chemicals and equipment now.

[jlewinsk]

Thanks for the quick replies guys. Excellent description, acidrain. Looks like there should be no problems at least dimensionally, by doing this. I'm still a little concerned about the effects of the acids, along with electrical currents running through the part(s). Maybe I'm just being paranoid, but it seems that this MUST be doing damage to the part on a molecular level.

PBinferno, you mention that you've seen this done to other cars. Were these show cars, or did they actually get used on the street. Were they professionally built or just some backyard garage hacker like myself?

Maybe I should quit worryin' and just get on with it...

Do you guys mix custom colors for customers and store them, or do you remix as needed? I'm asking this because the local guys run just two or three colors and charge ALOT extra to run a small batch of a custom color.

[destroyer125]

The parts are only damaged when they are not stripped correctly. As the coating grows, it digs rootlike streaks into the surface, further strengthening the coating and allowing it to permanently bonding with the part.

Color mixing wise- most colors can get an entire selection of shades of that color, so mixing colors like paint is not nessicery. Mixing colors for customers isnt usually cost effective, as the dye lasts for a very long time, and you end up mixing enough to do thousands of parts, but you only do a few. Different dye manufactures make their own shades and colors, so shopping around can usually get the color you need.

[hvacman250]

Thread hijack

Out of my curiosity, and maybe this can help some beginners:

What can you do to strip wrong other than leave it in there WAY too long?

Can one of you ano "experts" make a semi-detailed step-by-step instruction on how to strip?

[acidrain]

I always strip one part at a time, or at least on a assembly line. By that I mean drop one part in, give it a quick scrub, watch it. If you have small parts and can manage to keep track, you can drop a second one in at a timed interval (and maybe a third and forth) before the first part is ready to come out. This is risky though... if you loose track and leave the part in too long, it could become pitted.
1) De-grease the part... this will allow stripper to get to all areas, and you won't have to work at one tiny area left un-stripped while the rest of the part slowly disolves away.
2) Keep the stripper at the right temperature... I like 70F. Increase just 10 degrees, and there is a good chance you'll pit the parts.
3) Use fresh stripper... if it's week, you'll need to leave it in longer, or heat it up a bit. The chance that the part will be stripped un-evenly is higher with week stripper.
4) Rinse well... spray rinse coming out, then submerge completely. Swish around in the rinse water to rinse completely.
5) De-smut imediately after all the parts are stripped. If you just drop the parts in a bucket of water after stripping, the stripper will continue to work. The de-smut neutralizes the stripper. I always de-smut after stripping (even if there is no smut), then the parts can be dried for the buff or beadblast step.

[hvacman250]

Hhmm...I'm starting to hit a few roadblocks after a few months of awesome results. I'm starting to wonder if my stripper is damaging parts.

Its a few months old, and has probably stripped a few hundred parts. Does it need to be replaced yet? It still works, per se.

I clean the part, drop a few pieces in, wait a minute or so, then scrub with a toothbrush. Back in and scrub until all the dye is gone. Rinse good then desmut. It probably stays between 75-78* in a semi-cooled garage. Average time stripping is 5-8 minutes.

If the part is pitted, do you see pits in the aluminum? Like visible stuff? Can the part be salvaged from pitting?

Here's a problem I encountered last night:



Click on pic to make it bigger

Appears to be 6xxx aluminum, stripped fine, but came out of ano weird. Looks liek flaking in the metal itself. Scaly almost. Any ideas?

I'm getting a gut feeling something has changed. I was wondering if it wasnt my acid bath, but Im starting to blame the stripper. Kinda confused ??

[destroyer125]

Ive found you can determine where the pit came from by looking at it. Pits from the stripper tend to be deep, straight into the material, while pits from the acid seem to be somewhat shallow, and are kinda of grayish craterish

Weak stripper is bad news, ive found that out the hard way.


Your cocker body above looks like it has a grain. It would need to be reblasted/repolished.

Desmut and stripper can both bring out a grain in the part. Bob long clamshells are bad about it.

[PBInferno]

Originally Posted by jlewinsk

PBinferno, you mention that you've seen this done to other cars. Were these show cars, or did they actually get used on the street. Were they professionally built or just some backyard garage hacker like myself?

I've seen this on both show cars and really upgraded street cars. The show cars were built professionally, but the street cars were built in garages (they had anodizers do the parts though).