Wednesday, 28 September 2016

Tef - Gel Vs Duralac

Are some of us following the flock and not asking the right questions.

Tef - Gel vs Duralac, appears to be a debate

Does it have to be a choice? Perhaps the correct answer is to use both in the right application.

I have had several rigging problems I would put down to the use of or should that be misuse of Tef-Gel. Don’t get me wrong it’s a great product, but now it gets used in applications it wasn't meant for or was appropriate for. I know this because once I started to have problems I asked around and had similar stories told to me.

Having just completed several long passages, you can imagine my horror as I needed to keep re-tightening nuts and screws on the rigging during a passage. Then the odd machine screw and bale rained down from different parts of the rigging mid ocean. Yes I would say it was lube crated failure.

There are a lot of places on a boat where you need a galvanic barrier. At the same time, there are applications where you want that electrically isolating barrier and absolutely need fasteners to stay put until you put a spanner, screwdriver or hex key on them. Other times you will need an electrically isolating barrier and want the fasteners usually stainless to not gall or seize when hardware must be dissembled.

Duralac is a chromate containing jointing compound designed to inhibit electrolytic decomposition between dissimilar metals. Duralac is a free flowing paste based on a synthetic elastic resin and barium chromate. This elastic resin when set acts as a thread locker and at the same time keeps electrolytes from entering the interface of the metallic surfaces. The thread locking properties is not listed in the product description but as we have found out is very effective.

The function of Tef-Gel in eliminating dissimilar metal corrosion is the elimination of electrolytes from entering the interface of the metallic surfaces. The product information states Torque requirements may have to be altered according to application of thread lubricants e.g. tef-gel.
Alter the torque settings on screws going into aluminium they say. Well I am a fairly big bloke and am not afraid to crank the spanner that last little bit. But I won’t go to the next step and put on a helper bar over the spanner.  If I need to apply that much torque then it must be coming close to stripping the thread in the hole or shearing off the bolts and or screws.

If you are not worried about the part turning or want it to turn (think turnbuckle) then Tef-gel is great. If it is a fastener you want to stay put but still be able to remove down the road then Duralac is great for things like machine screws in the furler, boom fittings, spinnaker bails, screws holding on spreader lights and pin keeper screws up a rig.

I use both, each has its benefits but they are not interchangeable.

Yes Duralac jointing compound is a hazardous product, just like a lot of products we use for vessel maintenance. But don’t let this stop you from using this product.  Read the MSDS which is available on line.  Do a simple risk assessment and put in control measures.  Then there is minimal danger unless the simple safe working procedures are not followed. 

For those of you who are blindly following the flock and falsely believe Tef-gel is a totally safe product to use and no safety measures need to be put in place. Please read the product Safety Data Sheet or Material Safety Data Sheet (SDS or MSDS) again available on line. I know the control measures to work with either product are very similar.   

I have also heard the argument for using Tef-gel is due to its non polluting properties and Duralac will kill the environment. I am not sure who thought this one up. However if you think about it neither should be used in a manner that will cause pollution. Both are man made products, so clean up after use and dispose of the waste properly. If used correctly the risk of marine pollution from either product is almost zero. 

So back to our trip, once we were anchored and rested up we took stock of the situation and reassessed what needed to be cleaned up and have Duralac jointing compound applied. It did take a bit of doing cleaning up the threads and screws with solvents. However since doing this we have logged over 3000 nautical miles and nothing has come loose. 

As a side note, one of the bales I am talking about coming loose was our spinnaker halyard block bale at the mast head. It did had new nyloc nuts fitted because it was replaced prior to leaving Brisbane for our run up the coast.  So perhaps its time to look at the use of nyloc nuts differently when using thread lubricants. 

Other items to keep in the tool kit are thread locker and the most recognised brand would be Loctite, but I do know most generic products work well. A simple example is Blue Loctite. Works great on threaded parts that you need to take apart later, but can't have coming loose. And you'll notice that Harken includes little tubes of it in with a lot of the furler hardware which they sell.

If you’re assembling the anchor swivel and don’t want that little machine screw falling out in the middle of the night then red Loctite is what I would use. However it is more than likely heat (blow torch) will need to be applied to aid disassembly later, however the good news is that if the instructions on the bottle were followed it’s highly unlikely it will ever come loose on its own. 


  1. HI Matilda,

    Could u let me know out of following which one will be best and cheapest for anti corrosive(galvanic) and anti fouling grease? Molykote 111 is not performing well and I want that it also washes off not that very easily and not that very hard so something in between? Condition---sea warm water.

    Lanokote (newer version of lanolin for under water application)
    Tef Gel Sialkote (over hyped or does it worth the price?)
    Molykote 111 - is not working for me
    Loctite Blue 243

    Ancient mariner
    (On a memorable fishing expedition)

  2. Hello Ancient Mariner.

    I have used Molykote 111 on several occasions and yes it does wash off in a short time when used under water. I did give Lanolin grease a go as well but it didn't perform as well as the 111.

    I have heard good reports about Lanokote, however I am not sure about vessel usage. I think Prop Shield could be some thing you may want to have a look at, its grease/anti-foul coating. I don't think this can be applied when the boat is in the water, and needs some elbow grease to burnish the coating after application. But I know another cruiser who is using it and likes it.

    Best Regards,

  3. Hi,

    What would u recommend for something under water. I have corrosion and fouling in flanges and I would like to prevent that for lasts say weeks to months. Tef Gel I feel is over priced but I am not sure if Lanokote, Mclube Sialkote is as good as tef gel and for underwater application.