Flux for aluminum in Europe? - Page 1
Forum section: electronics / beginners

author: Kira
author_rank: Newbie
timestamp: September 16, 2025, 03:36:26 am
content: Hi. I am now living in Hungary, and I need to solder some aluminum.Some magic metal small radiator.Stuff that ALU PCBs made from.And 6000 mark...I know fluxes in former USSR countries...But what I can get in Europe? I tryed to search and failed, I dont know what should search for?There probably well known and cheap compound in Western word...

author: Kira
author_rank: Newbie
timestamp: September 16, 2025, 03:38:54 am
content: I have some paste that states it for aluminum, but, it does nothing 🫠As I saw on YouTube, there must be bubble action when proper stuff is applied.

author: tszaboo
author_rank: Super Contributor
timestamp: September 16, 2025, 10:53:18 am
content: I guess something like this?https://mesterekboltja.hu/alu-forr-aluminium-forraszto-szett-fluxcool-7575QuoteSo I guess copper or inox to alu soldering is possible. Never tried it myself.Sok szererncsét.

author: MathWizard
author_rank: Super Contributor
timestamp: September 16, 2025, 03:20:39 pm
content: What is the metal braided wrapping around typical coax cable ? Is that aluminum or steel ? Any time I've had to do something with coax or sheilded cables in general, I can never solder onto the shielding. One thing I made just has a big blob of solder like a doughnut, and the un-wetted shielding in the middle. I used a lot of aggressive RA flux, but yeah it's useless on those metals.

author: IanB
author_rank: Super Contributor
timestamp: September 16, 2025, 03:25:43 pm
content: Search for "aluminium soldring flux" and you will find some products. For example:https://soldersandfluxes.co.uk/product/tsc-alu-flux-aluminium-flux-150gm/https://www.harrisproductsgroup.com/en/Products/scaf4

author: wraper
author_rank: Unknown
timestamp: September 16, 2025, 03:29:53 pm
content: Quote from: MathWizard on September 16, 2025, 03:20:39 pmCopper, bare or tinned. If it's really tough to solder it, most likely it's an old tinned one.

author: Kira
author_rank: Newbie
timestamp: September 17, 2025, 02:18:42 pm
content: Quote from: tszaboo on September 16, 2025, 10:53:18 amYes. But. Crazy expensive. And no code so I can find in on mouser or something....

author: Kira
author_rank: Newbie
timestamp: September 17, 2025, 02:22:37 pm
content: It can be anything 🫠Try to cut piece of it and see on cut side color of metal.

author: tszaboo
author_rank: Super Contributor
timestamp: September 17, 2025, 04:32:02 pm
content: Quote from: Kira on September 17, 2025, 02:18:42 pmYeah but it is a webshop.I don't think you will find plumbing supplies on Digikey.

author: jjarvi
author_rank: Newbie
timestamp: September 30, 2025, 06:41:58 pm
content: Would Techno-weld do?You can also find some low temperature flux core mystery soldering/brazing wire from AE by searching 'aluminum welding rod'.

author: tooki
author_rank: Super Contributor
timestamp: September 30, 2025, 08:48:25 pm
content: Quote from: Kira on September 16, 2025, 03:36:26 amFelder makes it:https://www.felder.de/products/metal-construction-industry/soft-soldering/fluxes-for-aluminium.htmlThese should be readily available in the EU, since it’s made in Germany.

author: mtwieg
author_rank: Frequent Contributor
timestamp: October 01, 2025, 11:35:43 am
content: Soldering aluminum is not possible with the processes normally used for soldering copper. It is, of course, possible to join aluminum to copper and other metals, but this would normally be done via brazing or arc welding.If there is a way to "solder" aluminum (i.e. using a soldering iron, not a torch), it's not just a matter of using a special flux, you would also need a special solder alloy as well. I've never seen such a thing in real life though.

author: Ian.M
author_rank: Super Contributor
timestamp: October 01, 2025, 12:03:00 pm
content: On the contrary, it is quite simple to solder to aluminum with regular Sn60/Pb40 or Pb-free RMA core solder and a high wattage soldering iron, preferably with a tip in it you don't care much about! You need a freshly sanded or scraped surface to minimise the oxide layer thickness, then you must cover the area to be soldered with non-aqueous flux or high ignition point oil to exclude atmospheric oxygen, then scrape or abrade through the flux/oil pool to remove the oxide layer, then solder through the flux/oil keeping plenty over the joint, scrubbing with the bit to disrupt the residual oxide layer and extend the wetted area. Larger objects will need preheating *before* abrading through the flux/oil pool. Once both surfaces are tinned, you can sweat the joint together with ordinary rosin flux.

author: tooki
author_rank: Super Contributor
timestamp: October 01, 2025, 01:37:22 pm
content: Quote from: mtwieg on October 01, 2025, 11:35:43 amLiterally none of that is really correct.The only thing that is really different is the flux. Everything else can be done the same as with other metals.ChipQuik’s solder paste for aluminum uses Sn96.5Ag3.5 solder, which is an “old school” lead-free alloy. They do recommend a higher reflow temperature than would be typical for electronics reflow soldering.Can you solder aluminum using ordinary flux AND ordinary processes? No. You have to change one or the other.

author: IanB
author_rank: Super Contributor
timestamp: October 01, 2025, 10:10:03 pm
content: Quote from: Ian.M on October 01, 2025, 12:03:00 pmThis bit is pretty important. I have tried such experiments in the past, and while the process does work, it really ruined the soldering tip and it needed a lot of remedial work with tip tinner/cleaner to restore it. I have an idea to experiment with using a flame for the tinning part rather than an iron, since you cannot ruin a flame.

author: Ian.M
author_rank: Super Contributor
timestamp: October 01, 2025, 11:15:41 pm
content: A flame can't push solder around or rub the edge of the wetted area to disrupt the aluminium oxide where its been slightly undercut by the solder puddle, so you need much more aggressive, aluminium specific flux. Also note that the aluminum specific fluxes are very hard on soldering tips, far far worse than soldering under an oil pool or even than using plumbers acid zinc chloride flux.

author: IanB
author_rank: Super Contributor
timestamp: October 02, 2025, 01:26:39 am
content: The technique would be that you melt a blob of solder/flux on the surface of the aluminium underneath the oil and then scrape the aluminium surface with a sharp blade like a scalpel to expose the bare metal and allow it to be tinned. The item doing the abrading does not need to be the item doing the heating. In fact it is best if the heater is good at heating and the scraper is good at scraping.

author: mtwieg
author_rank: Frequent Contributor
timestamp: October 02, 2025, 12:32:33 pm
content: Quote from: Ian.M on October 01, 2025, 12:03:00 pmOh come on, even the guy who made the video is embarrassed at the result!Quote from: tooki on October 01, 2025, 01:37:22 pmPretty sure I tried this exact product years ago, and it simply did not work. But apparently it is REACH compliant, so it should be available in Europe!I've never encountered a flux which could reliably clear aluminum oxide reliably without very high temperatures or actively "scraping" the surface (i.e. not "soldering"). Maybe I wasn't able to heat the work fast enough to get it to wet before the flux was used up, thoughAlso please make sure to read the MSDS for these special products, and use proper ventilation. And be aware that the byproducts left over afterwards can be quite hazardous as well, both to people and to electronics. Proper cleaning is a must.

author: Ian.M
author_rank: Super Contributor
timestamp: October 02, 2025, 12:43:29 pm
content: Quote from: mtwieg on October 02, 2025, 12:32:33 pmYour second ever solder joint to copper was neat and tidy? If not, don't be so hasty to condemn his ugly joint to aluminum!He did miss an extra step that helps get neat results - get the aluminum tinned as he did, then remove excess solder leaving a generous coating (i.e. don't try to wipe it all off as the aluminum/solder interface can then oxidise and de-wet) which leaves you with a tinned patch you can solder a wire to neatly.