Touching up black anodized alu heat sinks

You're bound to get scratches and scrapes when you buy these in bulk. Even handling/installing them can result in occasional scratches. What are some good marker/paint brands for touching them up?

I suspect the particular black dye or concentration used for coloring after anodizing may play a part in this so a perfect match would be next to impossible in all cases. Nevertheless, something like a black Sharpie marker would be way off in most cases since it has too much purple in it. IOW, some blacks will be more suitable than others. Thanks!

Reply to
oparr
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" snipped-for-privacy@hotmail.com" wrote in news:1838bd41-e2b3-4f37- snipped-for-privacy@o27g2000vbd.googlegroups.com:

Staedtler permanent lumocolor black might be good. Experiment with rubbing or scratching with a fingernail right after applying to minimise it to only the scratch to be filled. If it fails you can remove it with isopropanol to retry or use something else. Those things are good for lots of stuff, filling tiny flaws in etch resist before etching (red resists ferric chloride better than black though), and for CD marking, drawing very fine tamper-revealing markings on fixings, etc.. I've tried several types but those beat all else so far. They're extremely good for darkening fine scorings on aluminium and stainless steel when marking out for machining.

Reply to
Lostgallifreyan

Well I was going to suggest a Sharpie but you can also get permanent ink markers for 'artwork' type use that have smaller tips and a denser dye. Staedler comes to mind.

Graham

Reply to
Eeyore

Aluminum oxide is as hard as diamond, fer christ's sake. It's not all that easy to scratch if you're moderately careful. And the color isn't something that's put on after anodizing, it's built in. There's some great colors available these days besides black, BTW.

You're right about one thing - a Sharpie doesn't match. But there is a marker out there somewhere that comes pretty close; it's advertised to match. Sorry I don't remember the name of it, though.

It might be careless design, but I've seen anodizing used as the sole electrical insulator in some applications. Touching up a scratch with a marker is obviously inappropriate for those situations.

Reply to
Smitty Two

"black anodized" is surely able to be scratched. "Hard anodized" is the one that is unlikely to get scratched, unless it was not properly applied.

Reply to
Archimedes' Lever

That is HARD anodized. A simple black anodized heat sink is NOT insulated at all. If it is insulated, then it is hard anodized.

Either way, your remark about touch up resulting in a non-insulative "repair" is true.

Reply to
Archimedes' Lever

That is HARD anodizing.

Hard anodized Al has a surface that is harder than steel.

That is NOT hard anodizing. Those surfaces CAN be easily scratched, and are NOT electrically insulative.

Reply to
Archimedes' Lever

The only difference between standard anodizing, and hard anodizing, is the depth. Standard anodizing is on the order of 0.0003" thick, while "hard" anodizing is on the order of 0.001" thick. They're both aluminum oxide, therefore same hardness.

Reply to
Smitty Two

"Hard anodizing came in three flavors at one time, and all three were depth related, and though the normal method is the same process, the fact that it is not done to a substantial depth, and the fact that that means it will have sparse surface coverage as well, means that one gets not insulative property, and next to no hardness gain. At least not enough to resist scratches as well as the mil spec methods do.

Reply to
Archimedes' Lever

Bottom line....I have several that arrived from the supplier scratched and based on the bulk pricing I received it would be somewhat absurd to request/ship for exchange. It is cheaper to just touch them up. Also, I need to machine them....It is cheaper to buy bulk surplus and machine than to open a new special order with the manufacturer.....Get the picture now?

.

Interesting....LOL!

Tell me about. I have an anodizing kit with several dyes and I know how to use them.

vertised to

Now you're talking....That's good to know and is exactly what I'm looking for. Thanks!

The Gecko 320 servo motor drive is one.

ituations.

I'm aware of that. Thanks!

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Reply to
oparr

Reply to
oparr

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No, it isn\'t:

http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness
Reply to
John Fields

I seem to remember seeing thin aluminum sheets with lots of oxide that were used as insulators for TO-3 size transistors. Does anybody else remember them or am I making things up?

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These are my opinions, not necessarily my employer\'s.  I hate spam.
Reply to
Hal Murray

In message , Smitty Two writes

Me too, on a NiCd discharger/conditioner.

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Clint Sharp
Reply to
Clint Sharp

Yes, those exist; the problem is, you need a mounting kit that insulates the inside of the TO-3 mount holes, because a steel fastener could nick the inside diameter and ruin your isolation. The mount hole fasteners aren't usually insulating, because that's the electrical connection to the collector/case. Teflon tubing on the bolt? Long shoulder washer through the heatsink and insulator and partway through the mount hole?

Insulator mounts for power transistors are sometimes more costly than the transistors.

Reply to
whit3rd

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