MAPP gas and aluminum: danger of melting?

[brownoarsman]

Hi all,

I'm trying to follow these disassembly directions from Haarken on my Mark 1 furler: https://youtu.be/jzcHvxBCjF8 in order to inspect and tighten my forestay.

Unfortunately, as we all know, with stainless steel and aluminium, two is company but when the third wheel of galvanic corrosion pulls up a seat at the table, well, three's a crowd. As a result, the torque tube screws in the clamp are frozen in place.

After checking the internet, I've been applying PB blaster for over a year, used an impact wrench with a thick bit, and have been applying heat to no avail. I've been on the phone with Haarken (great support!), and they said I've been doing all the things they would do. With the aluminum melting point at between 800-1200 degrees Fahrenheit depending on the alloy, I was playing it safe and using a small benzomatic butane hand held torch that should put out 2600 degrees. I've been thinking of hitting it with MAPP gas instead, with heat output at 3,700 degrees. The Haarken folks though didn't want to advise me on heat due to the danger of melting the fitting. Anyone have any thoughts on using MAPP gas in this application, and a duration of how long to torch the part, or any way of knowing when to stop before the aluminum melts?

As an alternative, there is a gap I can probably fit a Dremel cutting wheel into to shear the screw, and will probably only mar the torque tube clamp a little bit rather than melting it. Thanks for the help!

[capt-couillon]

Google "temperature stick" Stick melts at given temp. Commonly available from 100-700 F in 25 degree increments. Otherwise transition from solid to a nice shiny liquid is almost instant in aluminum with no lead up like in steel.

Personally I would go with the mechanical option. Drill and tap as required.

[Wotname]

Agreed that Al goes runny real fast without much warning - at least to uninitiated (like me ).

However I would try a bit harder with heat before getting the Dremel out.

I'm not sure what MAPP torch burner you have; some have a reasonably "broad" flame, others are much more pointy. If you have the broad type, there is less likelihood of doing real damage real quick.

I would play the heat around a largish area and take periodic reading with infrared type thermometer; just don't let the heat be too concentrated. By the way, don't worry too much about the heat of the flame (unless it is a pointy flame), it is the heat of the Al that is important. It should heat fairly quickly to start with and then the rise in temperature will slow down as the temperature differential between the object and the surrounding air grows.

Try to get the Al up to say 500F (or even 600F if you are game) and hold it there for a few minutes (max). Heat transfer though Al is pretty fast so that means the whole area including the screw threads should be around this temperature.

Now squirt some freezer spray onto the screw head and give them a good spray (maybe 20 seconds or more). I use CRC 300G but there are many types. Put the heat back on and get the temperature up again and repeat with the freezer spray. After a couple of cycles, let the whole thing cool to ambient and apply more PB Blaster.

Leave for a "suitable" time - like long enough to have lunch, a beer or coffee and a nap! Overnight is good!

Now apply some gentle heat to the Al, not much, maybe 150 - 200F, a quick squirt of freezer spray onto the screw heads and give it a good wallop with the impact wrench OR try to tighten slightly and then wallop it to undo it.

If that doesn't work, the Dremel is looking good.

The point is to try to expand the body and the screw and then contract the screw (with the freezer). After a few cycles, the corrosion interface might fracture enough to allow the PB Blaster to do it's thing. Reheating the body (only) just before trying to undo the screw also helps 'separate" the screw from the body.

FWIW, I have always found Reducteur H-72 way way way better than any other release agent or penetrating fluids (PB Blaster, WD-40, RP-7, Mouse Milk, Diesel etc). That is not to say that there isn't something better but I have to come across anything better .

No idea if it is available in the USA...

This stuff Reducteur H-72 busts myths about seized bolts

[brownoarsman]

Thanks for the advice couillon and wotname! It is precisely that rapid transition from solid state to liquid state that has me worried!

I was relying on the quicker heat transfer properties of aluminum vs stainless to break the corrosion, but the freezer spray is a phenomenal idea. I will try that approach with the MAPP and with the infrared thermometer or the heating strips as a last attempt before cutting. In retrospect, the little butane hand torch was probably not heating the torque tube assembly up too much given the wide aluminum body surface area and the small flame. Hot to the touch surely, but not I think in danger of melting.

Thanks again and I'll report back on how it went next weekend!

[paulajayne]

Warm it up.
Apply WD40

Warm it up
Apply WD40


Do this several time as it help to draw the WD 40 in.


RE Temp stick. Apply soap from a bar on it - heat up slowly and when soap turns brown STOP.

Repeat as required.

[captlloyd]

Harbor Freight has infrared thermometers, about $20 on a good day.

[denverd0n]

What I can tell you is that MAPP gas can very definitely melt aluminum. I have used it specifically to do that!

I suspect that drilling out the screw would be a better approach, if PB Blaster and WD-40 cannot loosen it.

[roverhi]

I've tried to melt aluminum with a MAPP gas torch without success. Not marine alloy but old Landrover aluminum. Might try the jumper cable trick to heat just the fasteners. That's worked a treat for me in getting SS fasteners out of aluminum.
Jumper cable trick.

You might try the jumper cable trick. Put a bolt in the postive lead of a jumper cable. clamp the negative as close to the offending bolt as possible. Touch the positive lead to the head of the fastener so you set up essentially an arc welder. It will heat the fastener to a cherry red if left in contact long enough. It works really well as you are heating just the area of the fastener and not burning up the surrounding area plus getting the fastener way hotter than you can with a MAPP torch. Other than using the trick to remove all the fasteners on 44 year old mast, used it to get corrosion welded bolt that passed through substantial aluminum castings on the self steering vane.

Having said the above, the hardest fastener to remove is not one that is threaded into aluminum but one simply passes through an aluminum casting like cleats, etc. Getting the bolts out of the self steering casting took something north of 25 iterations heating with the jumper cable and quenching with penetrating oil over many days.

[Pauls]

Good trick, Roverhi. That's a new one for me.

[a64pilot]

If the screw has a button head, you can sometimes get a pair of vise grips on it, if not then you can sometimes cut a slot in it for a regular screwdriver.
But impact will loosen it if it can be loosened, sometimes you can't and you have to resort to plan B.
Just if you break the head off, do not try an easy out, nothing will drill out a broken easy out, or no drill I could find would.

[yotscribe]

An old trick is to soak the offending bolt in vinegar; it eventually dissolves the corrosion that sticks the two components together?

[Lepke]

If other remedies fail, try a mild acid. Flush with baking soda & water to neutralize. When you put it back together, use some form of Never Seize.
Also turning a propane bottle upside down (so you get liquid), and spray on the screw head. An old trick to remove pressed on bearings.
I was a certified aluminum welder. The time between hot and melted is quick and to an untrained eye would probably ruin the aluminum part.
USS Belknap before and after an aluminum fire. Collision with carrier JFK in 1975. Belknap went under the deck overhang. Boiler exhaust heat started the aluminum.

[brownoarsman]

I quite like roverhi's suggestion for a number of reasons: pinpoint application of heat, no need to buy new equipment, and I have my Insight 12v battery on my bench right now charging up after the winter! And it sounds like a heck of a lot more fun!

Roverhi, the YouTube videos on this are all about linking a number of batteries together to actually weld rather than just heat, so not the direct how-to of this application. A few clarifying questions for you:
1) how long do you usually maintain contact on the fastener?
2) any protective gear necessary? (Welder mask, thick arm length gloves, etc.) Not sure how big of a spark this will make on contact.

Thanks!

[roverhi]

I just used the house batteries, 220 amps. Not scientific, just applied the clamped bolt till part got what I felt was hot enough, less than a minute. Could get the offending fastener glowing if the jumper cable was left on long enough. In short, you don't have to be all that fearful of damage, just use common sense. Did very occasionally have the bolt in the jumper cable clamp 'stick' to the offending fastener if I left it in contact too long. Just a wiggle of the cable clamp freed it. You do need to be aware as you are essentially setting up an arc welder.

No special gear necessary as you are just heating the parts. May be some gases created by heating any remaining solvent/penetrating oil but didn't notice it as I was working out in the open.

Someone turned me onto the trick, possibly on this forum, when I was having challenges refurbing the 40 year old mast on my boat. Twisted off a screw head or so using a 12v impact wrench. Was afraid I was going to be left with a bunch of broken off fasteners removing hardware from the mast. With the jumper cable trick and a bit of patience didn't have another problem with broken heads on fasteners into the mast. Removed all the fasteners without destroying the threads in the aluminum mast. Still have a few souvenir cleats with the fasteners firmly corroded into the aluminum that I'm saving for a snowy day to try the jumper cables on.

[zstine]

I think that vinegar is something to try and heating with electric is another option. In fact, there are induction heaters on the market for this purpose if the battery arc welder method scares you. If you are worried about melting the AL with MAPP, use a cheap propane torch as it is cooler and probably impossible to melt the AL. Another thing to alleviate your fear is to hold some Lead against the AL as Lead melts at just over 600F, way below AL's melting point.
good luck