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Blacking 'touchup' pot?

robtheplod

By robtheplod
in Boat Equipment

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system 4-50 Veteran II

system 4-50Donate to Canal World

Posted
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51 minutes ago, cuthound said:

 

That won't work If you have two pack blacking, unless you save some hardener saperately as well. ?

I understand that the small pot of hardener typically has a quite short shelf life, 12 months? Way shorted than the applied 2-pack that it is required to touch up? Can anyone confirm?

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blackrose Veteran II

blackrose

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Posted (edited)
1 hour ago, system 4-50 said:

I understand that the small pot of hardener typically has a quite short shelf life, 12 months? Way shorted than the applied 2-pack that it is required to touch up? Can anyone confirm?

 

I'm not sure if it's the base or the hardener (probably the hardener) but yes the shelf like of two pack is much shorter than the mixed/applied paint. Dr Bob is your man to explain why but I imagine it's something to do with organic polymer chains that won't cross link as effectively when mixed if they've gone beyond a certain point. I think my jotamastic has a shelf life of a couple of years but it's very much temperature dependent and I've used stuff that's at least 4 years old that's still fine because it's been stored on the baseplate in the engine space (removed when moving), much to the irritation of my BSS inspector. It's pretty easy to find out if it's still working properly. Mix a small amount in a yogurt pot and if it goes off solid all the way through like a lump of hard plastic it's fine. 

 

Always mix the base thoroughly before mixing with hardener and follow the manufacturers instructions on how to mix, either by volume or by weight.

Edited by blackrose
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robtheplod

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18 hours ago, john6767 said:

I have a big tin of Intertuff in the garage at home that came with the boat, I just fill up a jam jar from it that is on the boat and touch up from that.

thanks, I might need to splash out on a big tin and leave at home.....

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Dr Bob Veteran II

Dr Bob

Posted
Posted
22 hours ago, blackrose said:

 

I'm not sure if it's the base or the hardener (probably the hardener) but yes the shelf like of two pack is much shorter than the mixed/applied paint. Dr Bob is your man to explain why but I imagine it's something to do with organic polymer chains that won't cross link as effectively when mixed if they've gone beyond a certain point. I think my jotamastic has a shelf life of a couple of years but it's very much temperature dependent and I've used stuff that's at least 4 years old that's still fine because it's been stored on the baseplate in the engine space (removed when moving), much to the irritation of my BSS inspector. It's pretty easy to find out if it's still working properly. Mix a small amount in a yogurt pot and if it goes off solid all the way through like a lump of hard plastic it's fine. 

 

Always mix the base thoroughly before mixing with hardener and follow the manufacturers instructions on how to mix, either by volume or by weight.

Single pack paints always last longer as long as the tin doesnt let air in (most use air to crosslink). Yes, still usable in 10 years for touch up.

For 2 pack systems, the base or the hardner will have definitive shelf lives. The 2 pack system reacts by specific chemical reactions between the base and hardner but other reactions can progress ie with moisture or air that is in the cans when filled, or reaction of the active components with fillers etc in the formulation. The contents of the individual cans can therefore 'go off' so not be available for the designed chemical reaction. I've had epoxy adhesives that last 5 years but they wont be as good as new stuff. 2 pack epoxy paint may be ok for patching after a couple of years.

One issue is that a lot of manufacturers make 'low temperature' epoxies which are really a bit of a compromise using more 'active' crosslinking agents that cure quicker at low temps but may not get to the same cross link density as a 'normal' formulation. A draw back of these more 'active' crosslinking agents is that they could have lower shelf lives and only just last a year.

When I was involved in developing these products, we had a super duper oil tolerant 2 pack epoxy that was really stella in performance..far better than anything about today. Problem was that the shelf life of one of the components was 6-9 months at normal UK temps. That just wasnt acceptable for a commercial product. We pulled it!

For 2 pack systems it could be either the base or the hardener that has the shortest shelf life dependent on what the manufacture puts in each tin!

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Dr Bob Veteran II

Dr Bob

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23 hours ago, system 4-50 said:

I understand that the small pot of hardener typically has a quite short shelf life, 12 months? Way shorted than the applied 2-pack that it is required to touch up? Can anyone confirm?

Not sure what you are asking. I reckon even I could touch up in less than 12 months?

Being serious, you could have a 12 month shelf life for the individual parts of 2 pack system, but they could be 2 years. I doubt if they would be less than 1 year. Note however it all depends on temp of storage. Most will be tested at 23°C. It will half at 33C and double at 13C

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