Friday, November 23, 2012

Ion Iron

(Part 2 of the series, "Iron Man.") 
Chapter 94
This week continues our mini-series detailing my little holiday project: the inspection and restoration of an early '50s vintage model F50 General Electric steam iron. When we're done, we'll hopefully have brought a world-class shirtpresser back from oblivion, and ready for another lifetime of service.

Last week, we'd gotten the soleplate off, with its electric components, and figured out how said components work. The steel parts are all very rusty, and any attempt to remove them from the aluminum base is fruitless. We'll try to remove the rust somehow, and the easiest way to remove rust from parts that are rusted together, is electrolysis

Rust is the oxidation of metal -- a natural electrical process that can thus be reversed by artificial means. Basically, if the rust is negatively charged, (in other words, ionized,) and the rusty item is submerged in an electrolyte with a positive electric source, then the rusty ions will boil off the negative side and be attracted to the positive side. It's the same theory as with a vacuum tube, or an electric battery cell.

What we need to do first is to assemble a non-conductive container, an anode, some wire, the electrolyte, and a voltage source. Fortunately, all of these things can be made with simple household items. 

The container is simple enough -- a plastic office trash can can be used as a bucket. 

Next, we need a sacrificial anode, something made of iron or steel. The simplest and easiest anode is a simple tin can, cut apart and spread out like this, to expose the largest amount of surface area. Don't use anything stainless steel for the anode: the process will pull the chrome out of the stainless in the form of tiny amounts of chromium trioxide. It's very, very toxic. 

We need a hanging wire, to suspend the parts in the bucket, and attach the electric leads. A wire clothes hanger is perfect for this. Straighten it out with a pair of pliers, and bend it to shape. Suspend the anode inside the bucket, about an inch off of the bottom, like this.

Check the continuity from the end of the wire through the can, to make sure the electricity will flow...

...then bend a wire to suspend the soleplate inside the bucket. You want the entire surface and all the components to be electrically charged, so hang it from two points: one on the thermostat side and other on the base side. Use the continuity tester to make sure all points of the iron are continuous through the wire.

Next, we need to make the electrolyte. The best (and safest) electrolyte for the process is sodium carbonate, also called soda ash, washing powder, or Na2CO3. If you don't have sodium carbonate washing powder, don't fret: there is an easier solution. Baking soda is sodium hydrogen carbonate, also called bicarbonate of soda, or NaHCO3, which is a little less effective, but still usable. Better yet, take a quarter-cup or so of baking soda, scatter it on a cookie sheet, and bake it for an hour at 300° F. The heat releases water vapor and carbon dioxide from the sodium bicarbonate, and you're left with soda ash. If you remember your high-school chemistry, what you're dong is 2 NaHCO3(s) = Na2CO3(s) + H2O(g) + CO2(g). Voila, you've just made sodium carbonate!

Dissolve your newly-made soda ash in warm water, and submerge the soleplate completely. Now you're ready for the application of mass quantities of free electrons.

If you have an automotive battery charger, you're all set. This one is user-selectable to push 10 amps of direct current at either 6 or 12 volts. (This is another vintage item of mine; it's been ready to keep my batteries charged since the 1970s.) Newer chargers, with computerized innards that are designed to detect the battery's state of charge and modulate its voltage output for optimum charging, may not let you "repurpose" it the way we plan to do...

...which is this! Hook up the charger's clamps to the wires, outside the bucket. Remember the negative side is the cathode, (the iron's soleplate,) and the positive side is the anode, (the tin can,) since the goal is to move the negatively-charged iron oxide anions off the cathode onto the anode. Hooking it up backwards will run the process backwards, so make sure you have it the right way 'round.

Turn on the charger; start at six volts. You should soon start to see bubbles rising from the cathode, and the froth on top will start circulating around the anode. Rusty scum will float to the surface, heavier particles will collect in the bottom of the bucket.

Safety warning -- keep the charger well separated from the bucket. You're playing with electricity, so keep your hands out of the water. Do this in a well-ventilated area, or preferably even outdoors: electricity also cracks water into hydrogen and oxygen, so you want no stray sparks. Needless to say, turn off the charger before you remove the clamps. Better safe than exploded. 

Check the mix every twenty minutes. Strain the scum off, rinse off the anode (it will accumulate scum as well,) pour the electrolyte into a second bucket and discard the rusty buildup at the bottom. Add extra water as needed; you don't need to replenish the soda ash as it doesn't get used up. Electrolysis is largely a line-of-sight process, so turn around the soleplate to face the bottom toward the anode every other cycle, as shown here. 

If this were a solid chunk of iron, we could leave it boiling for days; when all the rust is gone the reaction stops. Since we have a chunk of aluminum in the mix, we have to be a little more observant -- the aluminum will keep boiling off without end. ("Boiling" in the sense of boiling off ions from the metal. The water may get warm, but it will not reach an actual thermal boil.)

After several hours of boiling in 20-minute segments like this, I noticed that the topside of the plate was not getting as clean as the rest of the plate. I checked the ohms again, and found that the top plate had lost continuity. This necessitated a shift in the wire, hooking it 'round the top plate until all points of the iron were again continuous. It's important to inspect your work every so often for this reason: if any part isn't getting electricity, it won't shed its oxidation.

As the anode collects rust, it will pass less electricity, and the amps will fall. This is the tin can after just a couple of hours. Keep an eye on the cathode -- when the bubbles start slowing to a trickle, bump the charger to 12 volts to keep things vigorous. When even that doesn't work, you might need to replace your tin can.

A sure sign that the rust is still falling off is thick yellow scum at the top of the bucket. Keep an eye on this as well. There will come a point when the yellow scum will stop in favor of grey scum. At that point, the steel de-rusting has stopped and the aluminum is boiling off. There may still be black rust on the steel parts, but the aluminum has become the easier reaction. There's nothing you can do at this point but keep a careful watch on the aluminum -- let it go too long, and it will start to pit and degrade!

How long to let the process go is a matter of judgement. I stopped after about four and a half hours of total boil-time. There's still a bit of black rust on the mounting plate and leads, but closer inspection shows that the loose rust and scale are gone. The aluminum is largely clean, but I daren't go any further for fear of pitting and degrading the base. When you've decided electrolysis time is over, rinse off the soleplate thoroughly, and dry it immediately under a hairdryer to prevent anything flash-rusting again. Dump out the water (there's nothing toxic there: just rusty water and washing powder,) and clean up -- you're done!

Now we can get a closer look at the soleplate, and do a bit of sleuthing. The reason this iron was donated to the secondhand store is becoming clear: it had at some point badly overheated. Perhaps the pivot got out of adjustment, most likely through the mounting arm becoming weak over time through innumerable heatings. Eventually, the thermostat was unable to cycle on and off: the pivot would simply give with the flexing of the bimetallic strip, and the iron was full-on all the time -- even when it was turned off.

The triangular steam box lid, held on by seven screws, and insulated with a steam-tight gasket, warped badly in the excessive heat. So badly, it sheared the head off of the foremost screw, and cracked the lid at the left-front screw. The pressure created by the warped steam lid on the point of the sole cracked it at the button slots as well, just adjacent to the steam outlets; (but these are hairline cracks that don't extend all the way through the base.)

The damage was probably caused slowly, and the iron used for a time in this condition, but the steam wore through the gaskets, and blew out and inside the body of the iron, rather than down through the sole. This caused the excessive rusting of the mounting plate just behind the steam lid, and deteriorated away the asbestos insulation. So from the original owner's point of view, the iron stayed on high and wouldn't steam well, and limped along until it was thrown out. Alas, a simple adjustment of an eighth of a turn on one screw would have prevented this.

Too bad for her, great for me...for this is very fixable. And next week, we will fix it, and get on with the project of restoration. Stay tuned!

Click here to go to the next essay chronologically,  Part Three of Iron Man.

Click here to go back to the previous essay chronologically, Part One of Iron Man.

Click here to go back to the beginning.

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