slurry brush? - Page 1
Forum section: electronics / general

author: coppercone2
author_rank: Super Contributor
timestamp: July 30, 2020, 02:53:05 am
content: So in the interests of flux welding and brazing, the ones where you make up a slurry or use slurry like premade fluxes (i.e. black or white brazing flux)What is a good brush to use? I already made the tool for holding the slurry (aluminum trough glued to a pedestal) for rod coating (that shit got everywhere with my 'dip in jar' technique and made a huge fucking mess), but I still don't have a way I really like for getting slurry on the work piece. I don't really like transferring the stuff by dabbing it with the welding rod.The flux is often more of a slurry that is a bit powdery (hard to explain) and I feel like normal flux brushes meant for applying acid/rosin fluxes for soldering are not good tools (their more like grease brushes, that stuff is 'greasy' because of the zinc chloride I think). The only way I have found to do it good is to dip the rod, then drip it off the rod on the work piece, then poke around until it gets everywhere. A pure zinc chloride flux is liquidy, but I think those flux brushes are centered on the stuff they sell at home depot.Is there a good small brush for applying this stuff? I felt like a BBQ brush (the silicone one) would be good, if it was tiny. The one that looks like cthulhu's beard. I would like the brush to be like, 1cmx1cm.Does anyone have any good tool ideas for this process? It's kind of like working with wet really fine sand or something. I would also like it to not corrode to shit when used with the salts.. they eat ferrous metal right up.

author: eKretz
author_rank: Frequent Contributor
timestamp: July 30, 2020, 03:50:07 am
content: Try an acid brush, that's what I use.

author: coppercone2
author_rank: Super Contributor
timestamp: July 30, 2020, 04:22:05 am
content: thats what I mean by flux brush (acid brush), their too dense with bristles to apply the slurry good. That thing is like a gel brush. I need a slurry/aggregate brush. Like something you put chunky BBQ marinade on with. (think fresh garlic and cut herbs, rosemary and red pepper flakes without food processor to make the food look good)I thought there might be a shrunken version of thishttps://www.belk.com/p/cooks-tools-silicone-basting-brushes/0438662259137.html?cm_mmc=PLA-GOOGLE-Belk_PLA_Low_Priority_National_All_Products-GEO_All_Products-0438662259137&s_kwcid=AL!5203!3!117040781968!!!g!297998419633!!92700049904982412&gclid=EAIaIQobChMIhoLWs5D06gIVloTICh0BiwKnEAQYAyABEgI8fvD_BwE&gclsrc=aw.dsI don't know if you ever mixed up aluminum flux, but it does not form a soup. If you want that nice thick visible molten salt to form, which seems to make the weld nice, you need to apply it only semi-dissolved. Then you cook it with the torch until it melts (like glazing). It does not seem to work well if you add a very thin layer. It is like standard sugar (not powder sugar).I am not re-grinding flouride salts to make a nice slurry!

author: KL27x
author_rank: Super Contributor
timestamp: July 30, 2020, 09:46:48 pm
content: Maybe you want some small silicone or plastic spatulas or spreaders. The type of things you'd use to smooth caulking or grout. To spread it on the parts. Then to smear it over the seams where you are trying to get the stuff to flow and form a filet.

author: KL27x
author_rank: Super Contributor
timestamp: July 30, 2020, 09:50:39 pm
content: Whenever I braze (steel), I face the same problem. Flux that is more like a solid or "wet sand." I typically scoop a little out with a knife and slap it on my project or table or whatnot, enough to do the job. So I can close the jar back up. Then I smear it into the joint with... my finger.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 12:01:33 am
content: yea its like trying to build a sand castle under water with the performance of these things.I don't think you want to do aluminum flux with your finger though (flouride). The one for brazing steel might be a bit better.I ordered an all silicone grill brush to try it, I thought I could try to cut it in half maybe to make it smaller and trim it down. (I like the ones I own so im not going to use them for chemicals)Maybe I will throw in a order for some kind of silicone spatula too. Need to find the smallest one thats a bit stiff.I feel like a ant eater in reverse doing this work.Also, I wonder if you can make a bottle dispenser for it. Like a flux dispenser (but you probably need to modify the nozzle, i expect massive frustration here). Or a syringe. I have a feeling a syringe won't be good to mix it in, but a small squeeze bottle might work. The problem is you always need to shake this stuff and mess with the water/powder content. And when you dip a hot rod into it, it evaporates alot of water.Thats why I made the rod dipper out of like 2 inch fairly thick (heat sink) aluminum angle iron and made it almost a foot long. The mixture is too inconsistent for a dip coating, you need to mess with it after dipping to uniformly coat it, and possibly dry it a bit with the torch before you weld.Do you use some sort of flux for actually gas welding steel, or do you just use the rods? I was using the rods bare (well, their copper coated) but this might be a problem.For brazing with cheap rods (phosphorus brass I think) I have some kind of powder, and for brazing with silver I have the goops (black and white goop). For aluminum brazing I have another powder (different then welding Al powder). I also have precoated rods (dynaflow and some kind of white powder covered ones (low strength) that work pretty good and burn green, so its probably boron based). I don't have anything for steel welding.What product should I try here for steel welding?? I thought this process was fluxless on the torch! (unless you mean stainless welding, something I have never done).https://www.quora.com/Why-are-no-shielding-gases-and-fluxes-used-by-gas-welding(however one post mentions its a borax process). If you have something I want to try it because anything helps with this gas stuff. I do see alot of rust burning away and making a mess during welding. Sometimes mild steel even sizzles as it is reduced by the gasses. I don't really like this.http://www.survivorlibrary.com/library/oxy-acetylene_welding-a_comprehensive_treatise_1916.pdfhttps://www.scientificamerican.com/article/fluxes-for-oxy-acetylene-welding/($8)The old book seems to suggest the same flux for welding cast iron should be used for welding steel if desired (sodium carbonate + bicarbonate) or some kind of more expensive proprietary mixture. I wonder if this information holds up to date with modern welding standards (i.e. xray inspection) since the gas process was phased out pretty quickly before the advent of modern technology used to discipline welds. Perhaps it offers a general improvement? (the proprietary ones seem to be a mixture of sodium carbonate and borax or just borax). It's claimed they require less use then carbonate/bicarbonate mixes. I assume high tech x-ray operators might have thought 'why bother' to dissect an old becoming obsolete process.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 02:21:54 am
content: I use boric acid based flux for silver brazing steel. The white flux.Flourides? Yeah, good call on not touching that with bare hands.I don't have a gas welder.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 02:31:47 am
content: I read braze as weld and thought you use flux for welding it, so i bought something quicklyso you will know what happens when you use cast iron flux on mild steel during gas welding soon enough :-/maybe you can throw it on if you need to rework something to avoid having to clean difficult geometries/deal with sizzle

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 02:45:29 am
content: Well, make sure you do it outdoors. The flux is supposed to liquefy at brazing temp. It's not supposed to be vaporized at welding temps.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 02:46:26 am
content: it says its welding flux (like anti borax no. 1)they seem to have different formulations for forge welding, brazing and gas welding.https://superiorflux.com/spec/TDS_Anti_Borax_No_1.pdfNot sure if they just leave the fuming detail out. I will take precautions . It seems to differ in the sense that they add borax to boric acid for the brazing flux, where the welding flux is just boric acid.Boiling point of boric acid - 300CBoiling point of borax - 1500C.It actually seems worse. I assume you would want pure borax, but maybe it reacts with the metal some how ? It says the boric acid is converted to borax as it increases in temperature. Maybe something more complicated is going on on a surface level. Someone on another forum wrote' have used it successfully. It doesn't bubble like laundry borax.' (something to do with hydrates )?https://www.iforgeiron.com/topic/20426-boric-acid-as-a-flux/at least its interesting lolI assume what can happen is that hydrates form when you evaporate it from water wheras boric acid might not make hydrates before it turns into pure anhydrous boraxBecause, the gas welding instructions say, to dip a hot rod in it, not to make a slurry. I.e. do not add water to it. It must mess with the dynamics. So, if you have anhydrous borox, and you do a rod dip, you are likely making a hydrate at some point in a shop (during container opening, leakage, moisture on rod), wheras with boric acid, you evaporate the water, are left with boric acid non hydrate, and it turns into anhydrous borax coating in situ, and its good because the melting point of borax is so high, and close to the melting point of steel, you cause problems during the welding process? Maybe what happens is, you have slight amounts of moisture on the rod and some hydrate contamination, so you are left with rust forming on the rod while its dehydrating the borax before its active. Not sure how many people are keeping anhydrous borax in dessicators prior to doing cast iron welding (I imagine a cowboy here repairing a horse shoe not a analytical laboratory).perhaps the bubble phenomena is beneficial to dissimilar metal brazing but not for welding (agitation).

author: pickle9000
author_rank: Super Contributor
timestamp: July 31, 2020, 04:06:23 am
content: Have a look at the 26minute mark.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 04:54:08 am
content: Re boric acid vs borax:That just means the "brazing flux" has water added and is partly dissolved into boric acid. This is the "wet sand" paste flux version that is white and clumpy. The dissolved boric acid cleans oxides at a lower temp, and the paste stays where you want it. After it dries out, the borax becomes molten salt at some higher temp by the time you reach brazing temp.The pure borax flux comes as a dry, white powder. You can heat a piece of metal to be brazed and stick it in the jar to coat it. (edit: well, maybe you are supposed to dip the filler material into it?) Or you can mix a little water to make it into a paste flux.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 05:04:20 am
content: but borax you buy will be hydrated (like epsom salt)*. If you cooked it at high temperature to dehydrate it, and stored it in a sealed container, it would be anhydrous borox. Anhydrous stuff in containers like ferric chloride does not really stay anhydrous after you open it, after a while you might see water pooling up. But you can't just dry it at that point, you need heat to dissociate it. It absorbs the water in a stable matrix. Not all salts do this. Table salt you can just dry up and its the same thing. But hydrate salts will permanently absorb the water until heated (like a dessicator). It can feel fully dry but there is a bunch of water in it (like cement).So if you decompose boric acid to borax, on the rod, the decomposition happens at 300C, where there is no water. So there is no foaming. It should just turn into anhydrous borox and stay that way until it cools down and absorbs moisture from the air. I guess what could happen is, a piece of not fully dehydrated borax could fall into your melt pool or in the fire and disrupt the fire/cool it/etc from losing water. Its so minor though. Similar to how you should bake arc welding rods in a special high temp oven prior to structural welding (xray critical inspected stuff). I think it has to do with porosity.I don't know what will happen if you take boric acid, dissolve it in water to make a slurry, then dry it up, then use it. I think it should still work the same, so long there is no borax in the boric acid to begin with.*I assume. The aluminum welding flux I got is sold anhydrous, but I don't think it will stay anhydrous. I sealed it with a extra piece of silicone self amalgamating tape around the lip of the jar to try to preserve it, but I suspect that if I want to use it in the 'sprinkle on' method for some reason, I should heat it in a crucible, melt it, crush it, and then sprinkle it on a preheated piece of metal, after its been sitting a while. I assume it also forms a hydrate since its sold as anhydrous. You can tell how anhydrous something is by measuring the water temperature raise.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 05:09:44 am
content: Copper, I think the borax is supposed to melt at brazing temp and cover the base metals. That's why the residue is like volcanic glass, because it melts. Maybe they add stuff to lower the melting temp. I dunno. I dunno what brazing temp is, just that I can reach it with a propane torch and it's around the temp where steel starts to glow red.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 05:12:03 am
content: If it is pure borax, without any boric acid, it will reach the temperature of dehydration (elevated) and release water vapor PRIOR to melting, turn into anhydrous borax, THEN melt. The boric acid is a stopgap measure in a mixture, but possibly a non-foam feature in pure boric acid flux.I Think anyway. this is not documented.So you put a slurry on, dry it out in a oven. You get a rod coated with hydrated borax. You heat it up, the borax loses the moisture at some critical temperature (it might have two temperatures, i.e. at temperature 1 : lose 3 water molecules, at temperature point 2: lose 2 more water molecules), then be turned into anhydrous borax. Then the anhydrous borax will melt.But in that time, you will have metal that was exposed to water vapor at high temperature as the borax hydrate is decomposing. And it might happen inside the weld area (say a chunk flakes off and gets sucked in). If boric acid is added, it will protect the metal (when it melts), but the borax will still lose water and still foam up, even if the metal is protected. I need to look at the temperatures of the hydrate dissosisation of the borax to make a time line. So that adds some kind of rust load that the flux has to clean that the flux itself made from activating because it activates hot. Kind of bypasses supercleaning metal a little possibly.Some lab procedures for fully dehydrating a substance are pretty gnarly, like 'leave molten for 30 minutes in a lab oven to remove all water'. Not sure what the hell happens inside of a fire whirl.If you some how say powder coat the rod with anhydrous borax, that may theoretically work better. Or dip it into a molten borax pool (scary). I think basically the fact that the flux is very active and that there is alot of it, makes the rust preload non issue, most of the time.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 05:38:33 am
content: Sure, sounds about right, I guess.Pickle, that was a cool example. I have never had to make a joint with that much strength:surface area. I've seen ToT make carbide tooling in a similar vein. I have only brazed crude instruments and framing. And a lot of bandsaw blades.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 05:58:02 am
content: The dry flux I have looks like salt. It's not sticky like ferric. There's no list of ingredients.It says to heat the filler rod and dip it to coat it.Suitable for brazing or for welding copper, brass, or bronze alloys. It doesn't mention steel (or cast iron), FWIW.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 06:01:08 am
content: I've heard of borax powder being used for killing bugs, too. You sprinkle it into carpet. It's not sticky. Dunno if there's something added. I've also used borax to flux lead, and it was a dry clear/white tablesalt-like solid, IIRC.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 06:08:02 am
content: I have boric acid roach killer some where I think. But I think its also a bad idea because of recent research showing boron is not very good for you.big debatehttps://www.ewg.org/enviroblog/2011/02/borax-not-green-alternative-its-cracked-behttps://en.wikipedia.org/wiki/Borax#Possible_carcinogenI thought I saw something some where which had much more fear in the article.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 06:11:13 am
content: Quote from: KL27x on July 31, 2020, 05:58:02 amIt is confusing because the silver brazes (white and black) are sold wet as pastes, but the dry stuff you need to dry dip. I need to reread the containers I have to make sure I am using them correctly.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 06:17:51 am
content: All of the fluxes I have seem to say either. But the one I bought for cast iron says 'dip hot'.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 06:22:32 am
content: It could however be this:Thermal decomposition of sodium perborate involves dehydration and subsequent decomposition of the tetra(hexa)hydrate and occurs in three distinct stages. The first stage, loss of water to give the monohydrate, takes place up to about 150 °C; decomposition then takes place in two steps, up to and beyond 165 °C, to give sodium metaborate (159). The kinetics of this complicated multistep reaction have been studied (163).So what it could mean, that if you use hydrated borax, vs any kind of evaporation, is that the maximum temperature of the steel around water vapor is 100C (and likely less, since you are going to evaporate the water at low temperatures since its being wisked away by flames), wheras with the hydrated flux, you will get water vapor reactions at up to or above 165C, since the water vapor is being generated on the surface past 100C due to decomposition. It could rust more aggressively. Like it suddenly will turn into a vapor generator when it reaches 150C.

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 06:25:09 am
content: AFAIK, you can mix the dry stuff with water, dude. And tada, it's paste flux.Yes, reread the instructions. I think your cast iron welding flux is technically for brazing. I've never heard of actual welding of steel or iron with any kind of solid or paste flux. Maybe it would "work" but leave pockets of acid salt in the weld. Whereas in brazing, the capillary action pushes most of the molten salt out of the joint.I don't know much about acetylene torch welding, I thought you just used a neutral or slightly reducing flame. With stick, there's absolutely nothing special about joining cast iron with a weld. As long as you're ok with it breaking, later.The weld will be fine; it'll crack next to the weld.I've never used the black flux. That looks way more creamy and spreadable. The white borax paste I have won't paint on with a brush. Maybe it's just a matter of adding more water than what it came like. Or maybe they add some extra mojo to the black flux.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 02:21:36 pm
content: I added a capfull of distilled water to my white and black harris paste fluxes because they got old in the garage and got a bit chunky. I hope its OK, i read people keep rehydrating them.and about cast iron flux

author: KL27x
author_rank: Super Contributor
timestamp: July 31, 2020, 07:53:04 pm
content: Gas welding is cool stuff. If I ever learn how to use an acetylene torch, whenever I successfully use it I will always think how much I love it when a plan comes together.

author: coppercone2
author_rank: Super Contributor
timestamp: July 31, 2020, 08:19:30 pm
content: fun involves-re polishing nozzles frequently-scrubbing fire bricks-washing flux residueless critical when you make a hole in the garage door driving a armored van with guns blazing out of it thoughif you do it get alot of fire bricks (the hard ones) to work on and to lay hot objects on (they also save gas and money and time as insulators)

author: Cerebus
author_rank: Super Contributor
timestamp: July 31, 2020, 08:28:08 pm
content: Quote from: KL27x on July 30, 2020, 09:46:48 pmBy coincidence I found myself smearing on some aluminium brazing flux with a small polythene glue spreader earlier this week precisely because I'd run out of acid brushes and didn't want to subject even a half-useful ordinary brush to the mix of chlorides and fluorides in Al flux. I can't say that it worked particularly well - I'd have more success with an acid brush. I got by, but it was awkward; kind of had to scoop up the flux slurry and tip it on, and then push it about to get it to where I wanted it.This kind, not recommended:

author: eKretz
author_rank: Frequent Contributor
timestamp: August 02, 2020, 04:08:56 pm
content: Quote from: KL27x on July 31, 2020, 06:25:09 amThereisactually a special process for stick welding cast iron if you don't want it to crack. It needs to be preheated to a minimum of 450° and kept there during welding. Welding should be done with nickel rod, something like Ni-Rod 99x or Crown 295, and peened well after welding. After welding, the part needs to be brought down to room temp slowly - if no ramping furnace is available, it should either be placed in a drum of preheated sand or placed in an insulating blanket. I've even set parts in the embers of a fire and covered with fire brick in a pinch. Just finished a weld repair on a dump truck hub a couple weeks ago. It's holding up fine with no cracks.The black flux stays stable at high temperature longer. It contains boron powder. It can handle a little more contamination before it's used up than white flux also. And KLX has it right, the powdered fluxes can be used by dipping in a heated rod or by making a paste with water.

author: Cerebus
author_rank: Super Contributor
timestamp: August 02, 2020, 04:38:10 pm
content: Quote from: eKretz on August 02, 2020, 04:08:56 pmInstinctually, that sounded unlikely to me (elemental boron is relatively difficult and expensive to produce) so I went and checked (source:Stay Silv Brazing Flux MSDSdata for both white and black flux). Yup, Potassium Borates, Potassium Fluorides, Boric Acid and actual Boron powder. Looks like my instinct was wrong.