Corroded Mast Boot

[redhead78]

hi all I have removed my mast boot and it is looking pretty rough, I scraped an chipped off most corrosion,still rough.I would like to get it as clean as possible the I will paint it. Also there are 3 4" alum bolts frozen in the slots, I used pb blast and impact driver, can I use heat on same metals, will it weaken the aluminum...Thanks Red

[skipmac]

Hi Red,

From the photos I think you mean the mast step, not boot. I am guessing the plate in the photos is bolted to the keel and the bottom of the mast is sitting on it?

Also, the bolts look rusty so I am guessing they are not aluminum but steel bolts, maybe stainless steel which will rust in the right situation.

Heat will be OK if you don't over do it. Also, try soaking in PB Blaster for a couple of days with occasional tapping on the bolts with a small hammer. Maker sure to put a nut on the bolt before tapping in case you damage the threads.

[Reefmagnet]

Direct the heat at the screws - it will be the thermal shock that weakens the corrosion bond. If directing heat at the aluminium be a little careful as it can melt, without warning, even from the heat of a primus torch.

Here's another couple of other ideas to help break them loose if you have access to the gear:

** Put two nuts on the thread tightened together and use an impact wrench (rattle gun) to try and break the bolt free from the corrosion on the base (have the gun set in the tightening direction).

** Use a socket behind the heads of the screws that will support the base around the screw head while allowing the screw itself to drop into the inside of the socket once loose. Give opposite end of the screw a rap with a hammer.

FYI I restored a corroded cast aluminium mast base on my previous boat that looked pretty much like yours. If I recall even the bolts were an exercise to remove too. I power wire brushed it to clean it, filled all the pitting with epoxy filler then fared, etch primed and painted. Came out looking brand new and stayed looking good for at least the few years I owned the boat.

[delmarrey]

If it were mine I would soak the screw heads in diesel for a couple hours then twist out the screws. Then have the plate sand blasted and then paint with an epoxy white paint several times.

When reinstalling use lots of 3M sealer around the screw heads. When mixing SS and aluminum, the aluminum acts as an anode. Thin plastic washers under the heads work well too, or both.

The casting looks pretty good but you do need a drain hole in the side for water to get out when it rains.

[brankin]

I saw this at Miller Bearing and would like to try it the next time I have a corroded part. The following is a cut and paste from their literature.

After you get the bolt out, I would powder coat the part and it will be good for another 30 years.
Hope this helps.
Bruce

Loctite® Freeze & Release instantly freezes seized and rusted parts (bolts, nuts, studs) down to -45ºF (-43°C). The
exceptional shock-freeze effect causes microscopic cracks in the layer of rust, allowing the lubricating ingredient
to wick directly into the rust by capillary action. The assembly can be easily dismantled after allowing 1–2 minutes
penetration time.

[delmarrey]

Originally Posted by brankin

After you get the bolt out, I would powder coat the part and it will be good for another 30 years.

Powder coating cast aluminum is difficult. The pours in the metal boil out when the paint is being baked on. It will leave a very porous finish, which will still corrode. And it not cheap unless you have your own equipment.