How does Duralac work?

S

Slocumotion

Well-Known Member
Joined
18 Jan 2013
Messages
180
Location
Orkney
Visit site
..and would something like this -
http://www.screwfix.com/p/la-co-sli...ml/53863#product_additional_details_container

- at half the price, be any use?

I've just taken all the (SS) fittings from my ally boom with the intention of refitting some, replacing others, and adding some more. There is some corrosion and a lot of white crumbly stuff. Is that the remains of the Duralac, or whatever was originally used, or is it corrosion product?
 
Duralac is messy stuff to use and difficult to clean up, (masking tape around the area is useful). It is of limited benefit where fittings are held in place by pop rivets or self tappers which tend to displace it. The corrosion of the aluminium in contact with stainless is a powder such as you describe. I would stick with Duralac if you must use a liquid product but sometimes an isolating gasket can be more effective. A tube will last for many years.
 
Last edited:
MikePalmer said:
..and would something like this -
http://www.screwfix.com/p/la-co-sli...ml/53863#product_additional_details_container

- at half the price, be any use?

I've just taken all the (SS) fittings from my ally boom with the intention of refitting some, replacing others, and adding some more. There is some corrosion and a lot of white crumbly stuff. Is that the remains of the Duralac, or whatever was originally used, or is it corrosion product?
Click to expand...

Duralac is barium chromate paste...

Barium chromate is very insoluble so will not be washed away

Hexavalent chromium is a strong oxidising agent and I assume this helps to stabilize protective oxide films.

A frequently suggested alternative is the Teflon based Tefgel. This works by simply excluding water from the joint

My understanding is that Tefgel works best with close fitting joints while Duralac is a better choice if the joints are not so close fitting.

I guess the Screwfix product is similar to Tefgel.

White powdery stuff in a joint between stainless steel and aluminium is most likely to be aluminium oxide resulting from corrosion of the aluminium..


Your choice but if the joints are a bit "gappy" use Duralac. If they are a nice neat fit leaving no gaps consider using a Teflon based compound
 
sailorman said:
Durlac like gorrilla glue is a messy as you make it.
Click to expand...

Well I'm pretty neat with most things but I find Duralac gets everywhere, especially when it's separated a bit in the tube and you get the thin stuff out first, and is very hard to clean up. That's probably a compliment to its formulation actually! If you can use it in your best suit without disaster - good on yer!

Never tried gorilla glue - maybe I'd better avoid it.
 
Troubadour said:
Well I'm pretty neat with most things but I find Duralac gets everywhere, especially when it's separated a bit in the tube and you get the thin stuff out first, and is very hard to clean up. That's probably a compliment to its formulation actually! If you can use it in your best suit without disaster - good on yer!

Never tried gorilla glue - maybe I'd better avoid it.
Click to expand...
I use duralac from a tin, its so cheap ( and marine / swindlery ) some waste due to forming a skin doesnt matter
 
AngusMcDoon said:
I have always found that after a few years it separates and when it is in a tube I've not worked out a way to recombine it. Maybe a tin of the stuff is easier because it can be stirred.
Click to expand...

Quite. For most of us a tube much smaller than the standard would actually be better even if the price per g was more.

On the separation issue, I've asked on here before about this, but without any really satisfactory answers. The bit that I find strange is that the solid part does not seem much drier than the original paste before separating, yet indisputably there is now a liquid part which has come out of the original mix. I use the solid bit while trying my best to mop up the liquid, but does the solid bit do the same job as the original mix? If so, what is the point of the liquid?
 
I've just been searching for cheaper sources of Duralac than the usual swindelries. I found this one, which seems to be aimed at the private aircraft market:

http://www.lasaero.com/site/products/article?id=P002OHHP1

They're significantly cheaper (almost too good to be true). Presumably when it comes to pricing owners of light aircraft aren't considered to be such mugs as yacht owners.

Has anyone ever used them?
 
My trick of avoiding the mess is to mask up, coat both/all surfaces to be protected with Duralac using a small brush and leave to go just past tacky-then it does not drip.

If a little yellow around the join is offensive, mask up close and remove the excess with the tape.

If you use it on a hot day directly from the tube it gets EVERYWHERE-ask me how I know......................
 
lpdsn said:
I've just been searching for cheaper sources of Duralac than the usual swindelries. I found this one, which seems to be aimed at the private aircraft market:

http://www.lasaero.com/site/products/article?id=P002OHHP1

They're significantly cheaper (almost too good to be true). Presumably when it comes to pricing owners of light aircraft aren't considered to be such mugs as yacht owners.

Has anyone ever used them?
Click to expand...

I've used them for aircraft spares, very good service. Watch their shippping costs though.
Very rare to find an aircraft place cheaper than a yacht place for anything but oddly I had noticed the Duralac discrepancy.
I see a 250ml tin costs less than a 115ml tube!!
 
Troubadour said:
I've used them for aircraft spares, very good service. Watch their shippping costs though.
Very rare to find an aircraft place cheaper than a yacht place for anything but oddly I had noticed the Duralac discrepancy.
I see a 250ml tin costs less than a 115ml tube!!
Click to expand...

I had hunted unsuccessfully for the shipping costs but I'll watch that. Thanks.
 
lpdsn said:
I've just been searching for cheaper sources of Duralac than the usual swindelries. I found this one, which seems to be aimed at the private aircraft market:

http://www.lasaero.com/site/products/article?id=P002OHHP1

They're significantly cheaper (almost too good to be true). Presumably when it comes to pricing owners of light aircraft aren't considered to be such mugs as yacht owners.

Has anyone ever used them?
Click to expand...

Interesting that it is described as zinc chromate in this link, even though the product information says it is barium based. I believe that zinc was the original composition, dating back 30 years or more, but most of the links I find now state that it is barium chromate. However, Googling 'duralac zinc chromate' finds plenty of hits, including this interesting one http://www.glosterairparts.co.uk/corrosion_prevention.htm
 
When I fixed fittings to my mast, I made gaskets from plastic milk bottles to go in between them and the mast. After 10yrs they are all still there and I can't see any corrosion.
 
You must log in or register to reply here.

Share this page

Top