Borax and it's effect on iron

[Gerald Boggs]

A while back, (Not on this forum) the subject of what effect borax has on iron over time was discussed.  I put forth that forged welded architectural ironwork that were welded with the aid of borax, needed to have the borax chemically removed (Vineger).  I was told I was wrong, that simply cleaning well with a wire brush was all that was needed.  
However, my personal experiences and the experiences of many other smiths, disputes this claim.  Rather then argue, I decided to run a test on the effects of borax on iron.  I forge welded three rings (I use them for crosses) One I vigorously wire brushed by hand.  The second, I repeated the wire brushing and then wire brushed with a wire disc on a angle grinder.  The third, I put overnight in vinegar and then washed in warm water with a little baking soda.

Here are the results after several months, left to right as written.  My experience says it doesn't matter if you wax or paint, it you don't do something beyond simply wire brushing, you'll get a build up of this white crud.

Exceptions to this: 
If I sandblast prior to painting
When I forge weld the reins on the tongs, I set the boss by heating and cooling in water.  I'm guessing the explosive reaction is akin to sandblasting.

I speculate that climate and humidity have a factor in this.
 

 

[John B]

When brazing, we used to wash the  borax off articles with hot water and dry them, this seemed to work, no need for vinegar which can cause corrosion elsewhere in the workshop and needs to be neutralised anyway  

[SimonW]

Where were the rings stored over those months, and what was the climate like at that time (if stored outside)?

[Frosty]

Borax is known for this and needs to be dissolved as it's in the join so brushing doesn't reach it. I've found how much residual borax is trapped in the weld depends on a few factors. The type weld, laps, faggot, and jelly rolling seem to be the most likely to trap flux. Butt welds and welds with round on round seem to be the least likely.

 

Borax is water soluble but being a base a little acid speeds dissolving. Dunking the join in water while warm accelerates penetration in the join by capillarity. As the iron/steel cools a vacuum forms in any voids residual borax in a join isn't welded steel so equates to a void. Just above boiling seems to be more successful then blacksmith HOT.

 

An acid will accelerate dissolving the borax but what I find works even better is something to help it break the surface tension, wet, a surfacant. A little dish soap, just a dribble is plenty or even better dishwasher rise agent, Jet dry being what we have in the kitchen.

 

Humidity will bake borax grow crystals making that fuzzy crusty white junk.

 

Some of the practices I've found limit "borax bleed out": (yeah, I just made that term up, please clue me to the correct one)

 

First I use as little flux as I can get away with. Seriously flux isn't glue all that's needed is an air tight coat. Unless you're welding dirty, scaly, etc. stock. In those cases you need enough flux to physically blast the crap out of the joint when you hit it with the hammer.

 

I don't weld dirty scaly rusty steel, I clean it shiny if possible. Then I flux it before I heat it, borax fluxes melt under 200f and if it has boric acid in it, under 140f. Once it melts the air can't get to it so I can't scale, rust, etc. Just a breath of flux think a coat of thin paint will do the job.

 

My next technique is the hammer pattern. My first blow is to the place most likely to trap flux. For instance a fold like a pattern welded billet, my first blow is right on the hinge to drive anything that slipped by me OUT.

 

On a lap weld, my first blow is as dead center as I can get with a turning face to make a 2D wedge of pressure driving the crap OUT. For long laps I will run a tattoo of blows down the center of the joint, reverse direction at the end and run one back up on one side, then back down the other side. I try NEVER to use a flat face, I WANT to see that shallow dent as the indicator the flux and any crud will be driven out.

 

Faggot welds are a little different but depending on the bundle the same rule applies, first blow in the center and work to the ends or sides.

 

After my first weld comes refining the welds, once again I try to use as little flux as I can. The came capillarity that draws water into voids will draw in molten flux. Of course that's the idea, you want to flux any cold shuts so they'll weld. About the third refinement weld any residual borax should be driven out of the joint and a quench and soak should do the trick.

 

A few drops of Dawn dish washing detergent or Jet Dry in the slack tub WILL make a big difference. Heck it'll even improve heat treat quenching as it breaks surface tension so bubbles either don't last past formation or don't form at all. If you have or get some "Sodium Laurel Sulfate" you have the probably most used surfacant around, good stuff we had a 55gl. drum of the stuff at the soil's lab.

 

Frosty The Lucky.

[Dan P.]

I generally don't suffer from this problem, but I'd be interested to have a read of the original thread. Any chance of a link?

[Gerald Boggs]

Where were the rings stored over those months, and what was the climate like at that time (if stored outside)?

Unheated shop, hanging up on the wall. Time: several months. Humidity is high in Virginia, this is part of the South. I do think heat and humidity play a big part. Most of the folks that claim not to have this problem, live elsewhere then the South.

When brazing, we used to wash the borax off articles with hot water and dry them, this seemed to work, no need for vinegar which can cause corrosion elsewhere in the workshop and needs to be neutralised anyway

I tried this once. If you recall a twisted basket railing I posted back in 2008? I think I read about it on Iforge and so scrubbed them off in warm soapy water. Less them a month after installation, I got a phone call from the clients about a white powder forming on the baskets. Cost me a lot of time (money) to fix them and I've NEVER gotten a single call from the (million dollar plus homes) builder for more work. Trying that little trick has probably cost me many thousands of lost dollars.

[John B]

Sorry to hear that Gerald, can only say what worked for me, mainly when brazing carbide tips to steel shanks for tools, somewhat easier to deal with than cages in pilasters.

 

Brazing/hard soldering is normally the only time I use borax, as a flux, so have never come across the problem in a forge weld I have done.

[Dan P.]

I find if I take the workpiece up to a heat where the borax is fully oxidized or  "dry", it should be nice and clean after a good brushing.

[Gerald Boggs]

When brazing, we used to wash the  borax off articles with hot water and dry them, this seemed to work, no need for vinegar which can cause corrosion elsewhere in the workshop and needs to be neutralised anyway  

12 years ago, I brazed a batch of lanterns together.  The gentleman I worked for has one hanging in his gallery.  I go out that way from time to time, next time I'll take a look.

[lupiphile]

My experience is exactly the same. On branching welds specifically, even when painted (xxxx, especially when painted). As for what I do about it, I dip every thing in phosphoric acid now. you don't need to rinse, and its safe enough to stick your hands in (rinse off afterward), Take care, Matt 

[evfreek]

I have this problem too.  The bad thing is that the creeping white shadow does not appear for months and is only visible after installation.  Often, it is so slow that the customer does not notice until a guest asks "what's that white stuff?"  Does acid really work?

[Gerald Boggs]

Acid works great. 

I've thought about using phosphoric acid for it's reported ability of converting rust into a protective coating that can be painted.
 

[Dan P.]

 As for what I do about it, I dip every thing in phosphoric acid now. you don't need to rinse, and its safe enough to stick your hands in (rinse off afterward), Take care, Matt 

 

I think it's important that we know what dilution you are talking about, for practical purposes, but also because I cannot imagine it is safe to stick your hands in, say, 85% pure phosphoric acid (or maybe it is?).