Zinc Chromate or not

[wooslehunter]

I just drilled out & tapped my alloy mast foot for new larger bolts that hold it to the mast. The threads had corroded away completely. The best way stop further corrosion seems to be to use zinc chromate paste.

However, to get access to where the cables come through the mast at the bottom, I need to remove the foot. This isn't very often but does need doing from time to time. How hard does zinc chromate paste go? If I use this on the threads will I get it apart again. Is there a better way?

 

[Gin]

I used zinc chromate on the join between s/s machine screws and aluminium window frames, then found I still had a leak a week later- there was no problem unscrewing the screws and resealing

 

[VicS]

No there should be no problem.
I use a homemade paste of zinc chromate mixed with linseed oil but the stuff you need to buy is "Duralac" paste which is generally readily available from decent chandlers. It is actually barium chromate.

 

[swampthing]

My mate works in aircraft maintenance and he gets me barium chromate, I use it allways now wherever stainless meets ally.It really does work. Wear latex gloves,its carcinogenic. Dissasembly no problem.

 

[srp]

If you dig around on this site you'll find Duralac and also Zinc Chromate primer in a spray can. I've just been sorting out my furling gear and some mast fittings, all of which have suffered over the years because they haven't been assembled properly - the white powdery corrosion between aluminium and stainless is extremely stubborn and often means that stainless bolts have to be drilled out.
I cleaned everything up, degreased it with hot caustic soda, sprayed it with zinc chromate primer, reassembled with new A4 fixings and Duralac, followed with a final coat of silver grey spray paint meant for alloy wheels. All these things are nasty to work with - rubber gloves, goggles, masks and working outside in the open air are a must in my view.
To answer your last question, Duralac does harden. Light Aero Supplies ( www.lasaero.com/ ) sell a much more expensive paste (not sure if it's zinc or barium chromate) which it says doesn't harden, but it's much more expensive (and my aero-engineer brother says it still hardens, just takes a bit longer!).

 

[JayBee]

Try Tef-Gel, it doesn't harden and is nowhere near as messy as Duralac.

 

[wooslehunter]

Done it with Duralac which I've used before. Didn't know it was barium chromate though. Thanks.

 

[VicS]

[ QUOTE ]
Didn't know it was barium chromate though. Thanks.

[/ QUOTE ] Commonly thought to be, and described as, zinc chromate. Maybe it once was.
Barium chromate is a slightly lower risk from carcinogenic point of view. (Carcinogenic if inhaled!) Very possibly that's because it is less soluble than zinc chromate but that's something I have not checked on. However it should still be handled with the same precautions.

 

[rogerthebodger]

Good day Vic hope you are well

safety info on Duralac

Technical info on Duralac