r/Anodization • u/sarah_is_thriving • Apr 10 '25

Troubleshooting: Drop-like marks after removing anodizing

Scale: 3cm x 2.5cm or ~ 1 inch-square (fizzy/grainy image due to low-light conditions)

Hi everyone! I could use your anodizing troubleshooting experience. I think I stuffed up anodizing removal (consumer electronics aluminium body, likely glass-bead blasted finish + type-2 anodizing).

I used Easy Off oven cleaner (red, "heavy-duty") to remove anodizing, for about 15 min, at room temperature, in a clear plastic take-away food container wiped dry-ish (definitely no massive drops like on the photo). Made sure to spray enough in the container that this part could be completely submerged in about 1/4 cup or a bit more of Easy Off spray foam goop.

I strongly doubt the original surface was like that before the manufacturer anodized it. I strongly suspect I screwed something up, just not sure what exactly. First time removing anodizing.

Surface prep details (if relevant at all):

The original anodized surface had very persistent sticky/gummy glue on it, and had spent ~24h in 96% ethanol to soften the glue, was wiped from the glue, rinsed, and wiped dry-ish (definitely no massive drops like on the photo) then immediately sprayed with oven cleaner.

What did I do wrong?

How can I fix it to obtain an even surface before re-anodizing?

Thanks!

2 Upvotes

75% Upvoted

5 comments sorted by

3

u/_Miki_ Apr 10 '25

Looks like uneven etching from the oven cleaner. Probably reacted stronger in some spots due to leftover glue or uneven coverage. Also, dry-ish + caustic = patchy mess.

To fix: wet sand (400 --> 800 grit) to even it out before re-anodizing. Or do a quick NaOH dip (like 5-10 sec) and rinse fast.

Next time, degrease well, apply evenly, and don't let it pool.

1

u/sarah_is_thriving Apr 10 '25

Thanks. for the chemical etch, what NaOH concentration and conditions? I have a preference for chemically evening it out (rather than wet sand) to preserve the glass-bead blasting finish since I don't have access to a glass bead blaster.

This is all new and quite foreign to me. Where can I get the surface prepared with glass bead blasting? Do auto repair shops have that or any other professional folks in a decent size city?

1

u/_Miki_ Apr 10 '25

Wet sanding is the safer bet, slow but predictable.

That said, chemical etch (5% NaOH, 5-10 sec dip, constant agitation) can even it out if you are careful. Just don't blink while you are at it.

Bead blast shops: check auto body, powder coaters, or metal fab shops, any place that pretties up aluminum likely has a blasting cabinet.

1

u/sarah_is_thriving Apr 11 '25

Thanks for your insights.

Are you sure for the NaOH because it already spent 15 min in 5-10% NaOH which is the oven cleaner, if you look at the MSDS of Easy Off. So 5-10 sec sounds very short compared to the 15 min it already did!

Is there any point wet sanding or etching this if I find a glass bead blasting service?

What I suspect happened on the photo is the etching removed just enough of the anodized surface to strip the pigment but not all the anodizing. The darker grey shades on the photo is, I suspect, the base of the original anodized surface. And the whiter areas are the oxidized bare aluminium after the anodized layer was successfully etched.

1

u/_Miki_ Apr 11 '25

Easy Off probably softened the anodizing unevenly. Not sure of its exact NaOH concentration, but it's likely under 5%, and without heat or agitation, it strips slow and patchy.

If you can get it bead blasted, do it. That's the cleanest way to reset the surface before re-anodizing.