steel bolts stuck in AL

If you heat them up with a blowtorch, you might manage to undo the bolts without damaging the thread. Sometimes heat can work wonders on rusty fasteners.

Best wishes,

Chris

I've had good luck with this with steel on steel. But I had a bunch of steel pipe in Al fittings a while back. This idea failed nearly every time.

Karl

Karl, Saving the threads, even if it were possible is a waste of time, because the treads have become aluminum oxide and have no residual strength anyway. Next time use anti-sieze at assembly. Most likely the fault was electrolysis, as they were probably diecast and zinc is often alloyed with the aluminum to promote flow in the mold. In the presence of water, the unit becomes thousands of little batteries. Steve

Heat 'em up , and hold an ice cube on the bolt . That's worked for me .

On second inspection; if I can't get the bolts out, it looks like drilling the next size and tapping won't work. I'll have to make all new. My version will be a bit beefier. What's the best bolt for AL with an eye on electrolysis? AL bolts are too soft in small sizes. Is stainless a good choice? or maybe brass?

Karl

Any alloy with significant copper in contact with it is bad news and will cause accelerated corrosion of the aluminium. Stainless is probably the least bad choice but even that is prone to seizing.

Karl, I run into this all the time.. .. .. and I've found out that the best solution (if you have the room) is to drill, tap and install a stainless Helicoil. A bit pricey, but ya only do it once. Ken.

On Sun, 7 Dec 2008 06:33:04 -0600, the infamous "Terry Coombs" scrawled the following:

We used to use inverted cans of freon for spot chilling. The Greenies would shit a brick about that today, not to mention the cost of R-12 nowadays.

-- At current market valuations (GM is worth less than Mattel) the Chinese government can afford to buy GM with petty cash. --Bertel Shmitt on kencan7 blogspot

Second that. I design a lot of aluminum heater blocks, etc. at work, and always specify stainless helicoils. Works great. I do the same at home. The 1/4"-20 tpi helicoiled holes in my flush kit clamp have been in a marine environment (dock box) for 3 yrs. and work fine.

A through bolt and nylock nut in the material of your choice, sleeved in a plastic tube and with plastic washers under the metal ones on each side? No dissimilar threads to corrode.

Won't work why? If it's because you can't go up a size, I'll give a hearty "me too" on the heli-coils.

Karl You work way too cheap. I would get new clamps. Ebay Item number:

Cut the tops of the bolts. drill as much out as possible, build a dam around the rest and dissolve out with diluted nitric acid.

Takes out the steel and cleans up the aluminium.

When re-assembling, wrap PTFE tape around the bolt threads, lessens the corrosion and aids disassembly. Alternatively, use low strength Loctite to seal the threads from corrosion.

Mark Rand RTFM

you're right, and if they were mine, that's what i would do. "The Kid" and I trade favors. But he don't buy for me and I don't buy for him. So, when he asks for me to fix something, I fix it. I'm going to helicoil for him. he buys the coils.

karl

The very first non-invasive step:

Kroil, PB Blaster.

Then, the other stuff. Nitric acid could work, as well, altho I never had luck. But it might do enough around the edges of the thread to free it up.

Is there something unique about diecasting alloys that make them prone to becoming "thousands of little batteries?" Leaded red brass (85-5-5-5; copper-tin-lead-zinc) is very durable in sea water, and is composed of metals much more widely separated on the galvanic series than aluminum and zinc, which are quite close to one another.

One of my clients (aerospace) uses Kingserts almost exclusively for this, with great success. I have no clue how much more expensive they are than Helicoil, but they look a lot stouter.

BUT, anything that's going to be exposed to real weather gets stainless to stainless (and lots of anti-seize on assembly).

Any bolt I remove or replace on my 15 year old RX-7 gets a coating of Nickel Neverseize prior to replacement. Do not use the copper based anti-seize compounds with aluminum or diecast materials.

General purpose stainless steel fasteners are a lousy proposition because they are too soft and gall easily. I have used high tensile stainless steel studs on exhaust systems but these are pricey.

For your application I'd use helicoils as suggested above and plated grade 5 bolts, along with a coating of Nickel anti-seize compound.

Wolfgang

Stainless is worse than ordinary steel for causing electrolytic corrosion, you need a metal with a valency closer to AL - brass is near, but any AL based alloy will be best.