Touching up black anodized alu heat sinks

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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!

 

[Eeyore]

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.

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

 

[Smitty Two]

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!

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.

 

[Archimedes' Lever]

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.

"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.

 

[Archimedes' Lever]

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.

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.

 

[Archimedes' Lever]

Aluminum oxide is as hard as diamond,

That is HARD anodizing.

fer christ's sake. It's not all
that easy to scratch if you're moderately careful.

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

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.

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

 

[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.

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.

 

[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.

"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.

 

[[email protected]]

Aluminum oxide is as hard as diamond, fer christ's sake. It's not all

that easy to scratch if you're moderately careful.

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?

And the color isn't something that's put on after anodizing, it's built in..
Interesting....LOL!

There's some great colors available these days besides black, BTW.

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

But there is a marker out there somewhere that comes pretty close; it's advertised to
match.

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

It might be careless design, but I've seen anodizing used as the sole
electrical insulator in some applications.

The Gecko 320 servo motor drive is one.

Touching up a scratch with a marker is obviously inappropriate for those situations.

I'm aware of that. Thanks!

 

[[email protected]]

Thanks all. It would be further appreciated if anyone knows the
details of the particular marker mentioned by Smitty Two above.

 

[Clint Sharp]

In message

It might be careless design, but I've seen anodizing used as the sole
electrical insulator in some applications.

Me too, on a NiCd discharger/conditioner.

 

[whit3rd]

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?

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.