I would like to remove the anodization from the shelf under mcpcb in the Manker MK34 for better heat dissipation.
I know I can sand it, but it takes a long time and it’s not the best way to keep the shelf even.
Oven cleaner does a great job, I use Mr Muscle but I guess any would do it.
@chatika vas paus, not too difficult: just make a concentrated solution of sodium hydroxide and you will be ready to go
Sodium hydroxide will eat the bulk aluminum too, and will liberate hydrogen gas in the process. Sanding is a much safer bet. If you use NaOH you’re going to be left with an unevenly pitted mess.
the sodium hydroxide, i agree, will make pits and the surface will be uneven and raw looking
I have used Professor Amos gel drain cleaner GEL and found it very easy to use. The gel is easier to use IMHO than the thinner liquid. It can be painted on and removes anodization in 2-3 minutes. Make sure you follow lye precautions, do it outside, and be aware sodium hydroxide and aluminum are exothermic. I have done several non-disassembled flashlights and had no problems with o-rings or buttons. It works better for flashlight removal than cleaning drains…
That’s pretty neat. Amazed it preserved most of the logo print. Do you treat it with anything after you remove the ano?
The SC31B picture is right after it got stripped. I did not remove any buttons or o-rings and they seemed to be fine. The gel makes it easy to paint on where it needs to go, but I left it on the threads on the head because they don’t show and it seemed like it wasn’t worth the risk.
I’ve used draino on plenty of paintball markers before I re annoed them and it has never come out pitted and unfinished looking. I guess if you dumped the part in a bucket and left it for a week or two but if you pay attention I’ve never seen it get messed up.
If you let the sodium hydroxide work in much too long you do get a rough surface and pits, but it is easy to find out when to stop. As long as the ano is not off, the reaction looks mild, as soon as the lye is working on the raw aluminium the reaction visibly speeds up with much more bubbling/sizzling. If you stop there (rinse the lye out) the surface is still smooth, and it takes quite some time to really spoil your surface if you keep on going anyway, timing is not extremely critical.
Btw, AFAIK no one has actually been able to measure how much difference removing ano from a led shelf makes in terms of speed of heat transfer, and given that an ano layer usually is very thin I would not expect useful gains.
^ this
If you really really want to strip the ano for your own piece of mind then go ahead. Even if you do end up with a mildly pitted surface that will be inconsequential (kinda like the ano).
There is a paper from last year that used an led specifically to test heat transfer with various forms of anodizing, but it was more interested in emissivity than straight heat conductivity. Interesting read. It may not transfer directly to this application in a flashlight head, but it found that every anodizing type was more effective than bare aluminum (again, emissivity the focus). I believe that was “bare” as in stripped and with a naturally protected surface, rather than freshly stripped for the testing. I was surprised to see the paper simply because a lot of that testing with same results has already been done by CPU heat sink manufacturers years ago.
I don’t think in this application that any differences will be meaningful. Also not meaningful, but when you remove the anodization you usually do open up pores that were created during the application process and then (usually) sealed again afterwards with a separate treatment. This will naturally seal off again with time, regardless of surface finish. I think any of that would be mitigated by thermal paste even if it were comparatively “rough” under a lens.
Some of this depends on the particular type of anodizing. Actual Type III “military” anodizing is a whole lot thicker than what we see on most of our flashlights and would inhibit conductivity somewhat (although being in direct contact under pressure as most mcpcbs are would make up for that a lot, I would think). The anodizing on most of our lights is comparatively cheap and thin to the point where it’s doing little besides holding the color. Some of the more expensive lights seem to have legit Type III anodizing but for the budget and mid-level lights, that process just isn’t in the cost.
Most heatsinks are fully anodised, even at the contact point where the hot stuff makes contact. Doesn’t seem to bother people.
You can, if you want to, but I kinda doubt it’d make much difference.
Ideally, for optimal performance in passively cooled lights, you want an black anodization(for maximum emissivity) and non anodized surfaces where direct thermal transfer is occuring.
Regular type II anodize is often ~.001” thick in total per surface, [.0254mm] with half of the buildup being external, and half being penetrative. Mil-spec Type III Hard anodize is twice as thick, .002” in total, [.05mm] again half/half external/penetrative.
It would not be difficult to test the difference between bare and hard anodize in regards to heat conduction. I am about to send some stuff out for hard anodize. I will include a square block with the lot. When it comes back I’ll machine a probe point equidistant from an anodized mounting point and an un-anodized mounting point. I’ll use a Fluke multimeter with a temperature probe and also a FLIR camera to track the die temps.
That’d be a neat experiment, maybe more directly applicable to flashlights…thanks for taking the time!
I think two thou is like the minimum for the military type III, no? And I think one thou is the upper end of the type II (I’ve read that it can be less than a tenth). I remember years ago before I knew anything about anodizing, I thought I’d buff off the color from some Easton arrow shafts. Boy, that was a mistake. lol. I was careful to remove no more than necessary (just emery on a medium soft wheel), but it left flat spots and divots…dawned on me that perhaps it wasn’t just a surface coating. 
Anodizing is hard and hard to sand evenly. Drain or oven cleaner can be applied as needed to weaken the surface to the point sanding is more effective. Stop when the color is fading and sand the rest to avoid excess etching.
Thank you for all the advice. I checked the drain cleaner on anodizing from another flashlight and it went away after about 10 minutes. The surface does not feel any rougher than it was before. I will try Manker soon
I successfully removed the anodization with the drain cleaner. The surface appears to be reasonably smooth and even.
I got my anodized parts back. I included the test block in the parts “lot” with a note saying it was not critical like the other parts, but for testing purposes. Well, it’s not exactly black, more brownish, and I can’t find the measurements I took of the block before sending it to anodize, so I am not exactly sure how thick this hard ano actually is. I could test it anyway, though the results will not be particularly conclusive. I figure the anodize company might have anodized it with the same parameters as one of the other smaller parts in the lot, or at least dyed it an insufficient amount of time, so the dye didn’t take too well.