Sharpies left permanent marks on anodized aluminium. Is there a way to clean it?

[ballen]

I often mark stuff up with Sharpies (permanent felt tip markers) before working on it. Helps me avoid stupid mistakes.

I just finished making up some splash covers from anodized aluminium angle stock. Normally I use isopropyl alcohol or acetone to clean off the Sharpie markings. But on this material, it didn't clean off completely: a shadow of the color is still very visible. Why is that? Is there a way to clean it off short of sandblasting it? I will eventually paint these parts, so it doesn't really matter, but I'd like to know for the next time....

 

[Finegrain]

Anodize layer is quite porous, so the Sharpie dye soaks into it. You can ask your anodizer to run a sealant process to make the anodize layer less porous.

Regards.

Mike

 

[MaxPrairie]

Anodize layer is quite porous, so the Sharpie dye soaks into it. You can ask your anodizer to run a sealant process to make the anodize layer less porous.

Regards.

Mike

Yeah, sounds to me like the aluminum wasn't sealed properly or at all. If you run your finger on the part it should feel soapy if it's sealed, otherwise it will feel stick. With parts I send out to get powder coat, they tell me not to write with sharpie on parts because it can bleed thru. Not sure if the same concern is there for paint.

 

[mjk]

I believe the Op is talking about using a sharpie during the raw and machining process prior to anodizing
There was a post years ago about this(I was part of the responses as I had similar problems)
Sharpie evan with acetone removal will still leave a trace
I use the blue, it seems to hide a little better than the black.
Once anodized its there forever

 

[CarbideBob]

Different color sharpies have different etching properties for some reason.
Red will permanently etch carbide, blue will not and black depends on how long left on.
We often have to color a part to see cleanup and you color more that where the new grind is done.
Red is only for a part that will never ship. That extra unground is not red after cleaning but it is etched.
I have no idea how this relates to aluminum. I was surprised to learn it in carbide.
Why would one color attack the cobalt binder more than another?
We clean these things in a row of ultrasonics, soap, phosphoric acid, water and more. 5 dips.
Not much porosity in carbide.
Bob

 

[sfriedberg]

I've never noticed the etching behavior, but I have certainly noticed the porosity. If Sharpie or other pigment gets into the pores of the anodize layer, it's really hard to get it cleaned out. Ultrasonic cleaning might get it out, if you have a tank large enough for the parts.

 

[fciron]

Why: As previously stated, the anodized layer is porous and takes dyes very well. That’s how all the colored al stuff is made, anodized then dyed the appropriate color.

As to removing it, perhaps more time in the solvent would get it out, but I wouldn’t count on it.

 

[ballen]

Thanks everyone, I'm 62 but still learning. This has been very helpful.

This is hardware-store anodised aluminium L-profile material, which I marked, then machined, then tried (and failed) to clean up.

Yes, the anodised layer has clearly not been sealed, does not have that glossy feel, so this is Sharpie in the pores exactly as described.

Parts are about 600mm = 2 feet long, too big for my itty-bitty ultrasonic cleaner. But frankly it doesn't matter, there is no point in trying to clean them up further, will sandblast, then spray 2k primer and PU paint. Sure, I'll watch for bleed-through but these are spray shields not car fenders so not very worried.

Executive summary: a good learning experience. I often use Sharpie to mark a part before grinding, will take a bit more care with that going forward.

Cheers,
Bruce

 

[boslab]

After anodising there’s sealing, if you don’t it will stain
Try acetone
Mark
Don’t write on exposed surface! I learned the hard way btw

 

[-cg]

It may not help in this case, but methanol works better than acetone or IPA for removing sharpie from hard surfaces.

 

[bsg]

DUH - my bad, I read it that you had done this PRIOR to anodise
So, for your "fix", try one of these and lightly rub with it (it has to be a fine grit rubberised block).
You will be utterly amazed at how these can clean up marks and make scratches disappear.
Klingspor SFK500 Abrasive Hand Block 120 Grit 1380| at Zoro

Cratex stick should work as well......

Polishing Stick Block – CRATEX Abrasives

Kevin

 

[boslab]

The mrs suggested what she called a garyflex blue block also, she was an inspector in the alu fab department, plus try it wet
With soap sometimes helps,
Mark

 

[ripperj]

Years ago we had to throw out thousands?) of Sharpies because they had Chlorides in them and could cause stress corrosion problems. I believe they changed the chemical makeup and I know you can buy Sharpies that are certified to be free of trace elements.

Zero idea if they would matter in this situation


Sent from my iPhone using Tapatalk Pro

 

[Yankee Metallic]

In my experience Lacquer Thinner works best on removing Sharpie marks. Better than acetone, denatured alcohol or BrakeKleen.

 

[mike44]

I use lacquer thinner to remove layout dies, Dykem and also sharpies. The lacquer thinner cleans the metal completely. Never tried it on aluminum that has been anodized but I think it will work.
I often use the large sharpie with the felt about 1/4" wide when a small amount of layout fluid is needed.
mike

 

[Yan Wo]

It may not help in this case, but methanol works better than acetone or IPA for removing sharpie from hard surfaces.

I prefer ethanol, AKA 190 proof Everclear, and I don't mean to drink. Available at your local liquor store. I get mine when we pass through Wyoming. It's cheaper there.

 

[ballen]

Follow up:

To satisfy my curiosity I tried various solvents and abrasives to remove the sharpie markings from the anodised surface. Nothing worked.

The parts (splash covers for a magnetic DRO scale, see my thread in Metrology) got wet-sanded with an abrasive sanding block and dishwasher soap, then sprayed with 2K primer and sprayed with 2K PU paint. There was no bleed through either the primer or the paint:

Thanks again for the helpful replies that I got to my question.

 

[gustafson]

Well, your experience sure taught me something, I shall be careful in the future with sharpies and anodized material

 

[ernieflash]

Another point on Sharpies if you use them to mark and then weld near them forget, it it permanent
I found that out using sharpies on Bright dip anodized pipe for tuna towers and such.
Could be a real problem on High end stuff. Just my two cents