paint stripping aluminium frame - Page 1
Forum section: electronics / general

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 18, 2021, 10:06:19 pm
content: I want to strip off the aluminum, the frame of the front panel of an HP 8595E, excluding sandblasting, I ask what other

author: jpanhalt
author_rank: Super Contributor
timestamp: December 18, 2021, 10:19:46 pm
content: Chemical strippers. Many contain methylene chloride, but if that bothers you, try plain acetone first. Some of the so-called "green" strippers contained 1-methyl-2-pyrrolidinone (years ago). That was not so green after all. I tried it once. Rather than cause a denatured paint that could be scraped off, it just made a goo. Anyway, after acetone/MeCl2, clean up with acetone or MEK to start anew.Edit: A poultice of NaOH/KOH will remove most paint. But, aluminum is amphoteric and will be etched a bit by those paint removers. That could be an advantage for subsequent coats, if you want a duller appearance.

author: coppercone2
author_rank: Super Contributor
timestamp: December 19, 2021, 12:30:40 am
content: the strippers now have a nitrobenzene or something that is less toxic then MC. They also smell 5x worse

author: DTJ
author_rank: Super Contributor
timestamp: December 19, 2021, 12:57:58 pm
content: Quote from: coppercone2 on December 19, 2021, 12:30:40 amI tried to clean up / etch some aluminium brackets years ago. I forgot they were in the (strong) NaOH solution for 3 days. It was 3mm x 10mm ally bar bent into a bracket. Almost the entire brackets had dissolved.

author: jpanhalt
author_rank: Super Contributor
timestamp: December 19, 2021, 01:57:32 pm
content: As I said aluminum is amphoteric. Strong bases and acids both attack it and cause "black smut" that can be hard to remove.Toxicities of nitrobenzene v. methylene chloride (Wikipedia):nitrobenzene:LD50 (mice) 750 mg/kgPEL(USA) TWA 1 ppmmethylene chloride (dichloromethane]:LD50 (mice) 1250 mg/kgPEL 25 ppm (long term), 125 ppm (15 minute)As for relative toxicities, make up your own mind. Use either with adequate ventilation.Older people may recall the wonderful smell of shoe polish prior to about 1960's. That was due to nitrobenzene used as a solvent in them, which has been removed.Again as previously stated, I like a paint remover that denatures and causes the finish to curl up, which can be removed with a plastic scraper to avoid scratching. Many of the green removers dissolve and make a sticky goo that is harder to remove.After using any paint remover, one needs to clean up with something like methanol, acetone, or soap and water. Every stripper I have used in the past 60+ years is compounded with an alcohol or other water-soluble solvent, so clean up on metal often can easily be done with soap and water.Have you thought about how to repaint it? HP finishes on frames and such often have a slightly crinkled finish that can be difficult to reproduce. For me, I would just leave the original and clean it well. Absolute ethanol or a quick wipe with a towel damped with acetone or MEK may work, unless it is worn through in places.

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 19, 2021, 05:13:19 pm
content: The paint is now missing in some places, I have a powder coating next to it, the final appearance would be similar to the original

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 20, 2021, 07:30:01 pm
content: It worked well by wrinkling the paint acetone, a fine brass brush and a lot of patience.

author: RoGeorge
author_rank: Super Contributor
timestamp: December 20, 2021, 08:01:53 pm
content: I wonder if paint would be scourged away from Al by heat, like it is scourged away from wood, with a heatgun, or maybe by baking the Al panel in an oven.

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 21, 2021, 11:41:29 am
content: I initially tried with the LPG torch for brass welding, apparently nothing happened, the paint did not even change color.

author: Nusa
author_rank: Super Contributor
timestamp: December 21, 2021, 12:30:07 pm
content: Heat and scrape works fast on painted wood, since wood is a thermal insulator and doesn't suck heat away from the paint. On metal, you have to heat up the whole area to get the paint softened. Once soft, it should scrape off. Don't forget the object is a touch hazard until it cools...free lesson in profanity if you do forget. If you're planning to repaint, wipe down with mineral spirits or equivalent to remove oily residues.

author: jpanhalt
author_rank: Super Contributor
timestamp: December 21, 2021, 12:33:41 pm
content: Another difference is that heat does not anneal wood, but can easily change the properties of a heat-treated aluminum alloy. So far as I know, heat is never used to remove paint from aircraft.

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 21, 2021, 09:27:37 pm
content: I solved it very well with acetone, now it's in the paint job, they think about protecting the parts of the panel that must be without paint with glass tape, the powder system uses a high temperature oven.

author: hnjmkl
author_rank: Regular Contributor
timestamp: December 24, 2021, 11:51:04 am
content: I realized that there is a restoration section, I had to post in that.