Soldering problem

Nice work.

Isn't the dissimilar metal problem gonna pop up sooner or later? Steel is gonna rust. What's the cost differential for making the whole disk out of brass?

Sounds like the goop was working??

Perhaps immerse it in hot citric acid solution for a while at the end to get rid of rust and flux remains. I've noticed citric acid is the wonder cleaning stuff - nonpoisonous, water based, cheap and cleans rust and flux away really well. Works fine for brazing fluxes too. It is the same stuff you use for cleaning your coffee making machine!

I even cleaned my WEDM water container with citric acid.. It was all green, rusty and dirty in the beginning with who knows what metal remains on the walls there. Few times of hot citric acid (as hot as water comes from tap, around 60C, and some citric acid to it) and it is the normal clean stainless steel colour on all walls again. Totally amazing!

Assuming that you are talking about soft soldering, that is: tin/lead solders---

The solution that I have used for the last 50+ years is this: Don't use acid based flux. Instead, I use rosin based fluxes or those that are used for electronic component soldering. You probably will need to practice your pre-cleaning a little, as the rosin based flux isn't as chemically active, but it'll work.

I know many tinsmiths who use acid based fluxes and then spend a lot of time and care to get rid of the acid afterwards. While I am not a tinsmith in any stretch of the imagination, the rosin core solder works well there, too. And no worry about clean up, even 'tho I do use acetone to clean off the "rosin" that shows.

Pete Stanaitis

----------------

Thank you.

I have had no problem with the glued pieces even after a relatively long period of time (indoors) and with relatively little surface finish protection (wax or even just Autosol). The dramatic part in this case was the rust appearing in less than 24 hours.

The Goop works fine (the *only* glue that would do the job BTW!) but it can take up to 72 hours to cure completely and allow machining.

As to the economics of the whole thing it is kind of complex: To get a similar size dial (2.5" diameter, 3/16" thick) the cheapest way would be to buy 2.5" round brass and slice it up. A very rough calculation making all kinds of assumptions about machining losses shows that my way is about 30% cheaper. I use 1" washers so a lot of cutting is already done. I could bring the cost down even further if I could get mild steel disks stamped out but when I tried this (at ridiculous shipping costs) it did not prove to be a free lunch either.

I have done many all-steel dials, too, and people seem to like them just as much as the brass ones. However, in the current economy, selling them at prices that would barely cover the costs is proving difficult. Hence I am looking for different methods of making them. It is a slow process :-)

Michael Koblic, Campbell River, BC

No doubt excellent for stainless steel. Unfortunately with mild steel all you are doing is activating the steel surface for further rusting.

Michael Koblic, Campbell River, BC

An old Gorton Pantograph and suitble small cutters? Cheap, easy

Gunner

The methodology of the left has always been:

1. Lie
2. Repeat the lie as many times as possible
3. Have as many people repeat the lie as often as possible
4. Eventually, the uninformed believe the lie
5. The lie will then be made into some form oflaw
6. Then everyone must conform to the lie

Indeed! And I can vouch for the "look them in the eye and ask" gambit.

Works nearly every time, no matter the situation.

Gunner

The methodology of the left has always been:

1. Lie
2. Repeat the lie as many times as possible
3. Have as many people repeat the lie as often as possible
4. Eventually, the uninformed believe the lie
5. The lie will then be made into some form oflaw
6. Then everyone must conform to the lie

Gunner on Thu, 10 Jan 2013 01:04:40 -0800 typed in rec.crafts.metalworking the following:

First Aid class we were taught "Point at someone and say 'You - call 911!'."

-- pyotr filipivich "With Age comes Wisdom. Although more often, Age travels alone."

In fights I pointed at someone and said, YOU! Call the coroner, your 'freind' will be dead in two minutes!

If I understand, you machine after soldering the brass to the steel. I have a lot of trouble believing that the acid flux would penetrate solid mild steel so far that peeling 0.050" off wouldn't solve the problem.

Use of rosin flux has been suggested, but that probably won't work very well for steel. The traditional dodge is to tin the steel using acid flux, wash the flux residue off with hot water and bicarbonate of soda, and then solder brass to steel with plumbers flux (intended for soldering copper pipe). Clean the flux off with acetone followed with hot water.

I have also soldered cadmium-plated steel by mechanical cleaning followed by soldering with plumbers flux.

Joe Gwinn

Not sure that I understand.

This will remove all the flux that is accessible but not the flux that is underneath the solder. My contention is that this "hidden" flux is then exposed by machining and causes rusting on the freshly exposed metal. One can argue that the cleaning should be repeated after the machining but because of other processes involved this is not feasible.

My understanding is that vast majority of plumbers' fluxes are acid based, or, to be precise, zinc chloride and ammonium chloride based. Mine certainly is..

Michael Koblic, Campbell River, BC

The acid cannot penetrate that far into the metal, so the rusting was from some other cause.

Said another way, if the acid did penetrate that far, you should change metal suppliers.

There is no flux hidden in the metal to metal interface between solder and steel. The solder displaced the flux, and/or entombed it, preventing access to the air.

The critical flux residues are elsewhere. That's the reason for the hot water wash and/or neutralizing bath (sodium bicarbonate).

That is correct. However, if you look at old copper plumbing, you will see that it doesn't matter. Soldering is a very old technology, having been used by the Sumerians in 3000 BC.

War story. Before I knew better, I built a Heathkit VTVM (Vacuum Tube Volt Meter) kit using plumbers flux and solder, using a 250-watt Wen soldering gun. This would be in the late 1950s. I still have that VTVM, and it still works. Also still have the Wen.

Joe Gwinn

Agreed.

Agreed again. I contend that machining exposed one of these "entombed" areas.

This was done after the soldering but before machining.

It matters if you solder brass to mild steel.

Michael Koblic, Campbell River, BC

Greetings Michael, I've been reading this thread about your soldering and how you mentioned using rosin flux. I was pretty sure it would work but I tried it any way. Soldering clean steel and brass was easy with plain old rosin core solder. After the first test I applied more solder to each piece, more than needed to join the two pieces, and then used a rag with lard on it to wipe away the excess and just leave a thin coat. Sorta like tinning a copper or steel bowl. I then cleaned off the lard residue with acetone and laid the brass on the steel, heated the stack, and then pressed down with a steel block to squeeze any solder out for the thinnest possible solder line. My little test worked well. Maybe you can use some of the above info. Eric

The entombed areas are very close to the surface, and with sufficient machining depth the tombs should be removed.

OK. That handles the surface.

Only of the environment supports galvanic corrosion, which may be the case. But this has nothing to do with flux products, which are either entombed (no access to the atmosphere or visibility at the surface) or removed and/or neutralized.

Galvanic corrosion can occur if a piece of steel is electrically connected to a piece of brass, by any means. Soldering works, but is not required. Bolting together would work too.

Another poster (etpm) said that he was able to solder brass to well-cleaned steel with rosin-core solder; this uses activated rosin (activated flux contains some kind of acid dissolved in the rosin). The end result is brass and steel electrically connected.

So, the deeper and long-term problem may not be how to manufacture the brass-steel composite per se, but rather how to control galvanic corrosion in the resulting assembly. Copper or brass or nickel plating of the steel component may be required. Or electrical isolation of the brass and steel components from one another.

Joe Gwinn

That is pretty much the procedure I used except for the lard :-) That in itself is an interesting suggestion. Would some other fat work or is there something magical about lard? Getting the thin layer is important as the squeeze-out is a pain to deal with especially if it gets onto the face of the brass dial.

The big issue in my case is to avoid shifting of the parts when one applies pressure with the steel (I used wood) block. Mine shifted only slightly and it was not a problem but I can see how next time I may not be so lucky.

Anyway, I now have a small bottle of rosin dissolved in 99% isopropanol (it was surprisingly easy). Time to have a go when I have etched another brass face.

Michael Koblic, Campbell River, BC

Lard was the GOTO leading element in high-end body work when I worked at the Frame & Collision Shop. It's evidently ideal for molten metal. It doesn't smell too bad, either. Like fried pork rinds. Anyway, they'd use wooden paddles with slightly curved ends, warm the faces in the flame of the torch to get them hot, dip them in the lard bucket, and it would come out dripping with lard for smoothing the thick metal they melted onto the heated fender. It worked great, and it's a real art. I think lard's the original flux. Eastwood carries the paddles if you don't end up making your own.

Look on the shelves at the market or ask a Mexican restaurant owner where to find some Manteca. He may give you a handful. (/nasty visualization) It's still available at most large supermarket chains here in the States.

Perhaps you could drop or mount them into a sacrificial wooden frame which would hold the parts aligned.

The more I think about that, the more I think it might have been tallow (beef fat) instead of lard that they used at the body shop. But lard may work as well.

Ya suren it weren't bear geaze? ;-)