thinking of buying epoxy mastic..any others around?

steveo3002 · Oct 20, 2009

ive got a few underbody touch ins to do on my 21 yrs old

been reading around and expoxy mastic 121 seems to be well reccmonded with no downsides

just wondered if anyone has anything good or bad to say about it , or would other epoxy primers work just as good ..as the 121 stuff is near £40 a ltr posted

MG David · Oct 20, 2009

You might want to see the following thread:-

http://www.mig-welding.co.uk/forum/showthread.php?t=11190&highlight=epoxy+mastic

I went ahead and bought epoxy mastic and used it. So far so good. I will be able to give you a better answer in 10 year time!

steveo3002 · Oct 20, 2009

whats it like to use?

how long does the mixed product stay good for?

any ideas if unused stuff keeps on the shelf for long? i doubt i will use it all and it would be a shame if it goes off

wyn · Oct 20, 2009

I bought some the other day to use on a chassis. I've only tried a small amount so far just to see how it goes. It was easy enough to apply with a brush.
I'm not sure on how long it is usable when mixed..I was worried it would go off a bit quick so put it on as quickly as i could.

Chipper · Oct 20, 2009

I like epoxy primer. Pretty cheap, sticks well, doesn't react or cause reactions later. I've used it on ally bike parts inc engines and exhaust cans, steel, fibreglass, and plastic bodywork.
Degrades in UV, but takes a while. My trailer was outdoors for 2+ yrs in bare epoxy before it started chalking.
Doesn't flow that great if brushed, but did my landy chassis part brushed, part sprayed.

Lechler is about £13 a litre I think plus hardener, there's a special thinners but can use 2k thinners, just seems to make it more gloss than the proper stuff. PPG epoxy seems to want more heat to go off hard so the Lechlers more convenient. Not used any other makes than those 2.

Mates use it on their rods & customs, both chassis and body.

steveo3002 · Oct 20, 2009

chipper im near cambridge too

do you think this lechler stuff is pretty much what the epoxy mastic is ...im thinking it might be ?

where do you buy it if you get it localy?

i dont really care how it looks , wont look as bad as rust lol ...and i'll prob overpaint it anyway

Chipper · Oct 20, 2009

Hi Steve, I used to go to Ketts at Peterbog, got an account there, or they'd drop stuff off as they do runs round our way anyway (drops didn't cost delivery either). Change of job means I can't nip up there daytimes anymore. Also went to Hugs or Nu-Agane or whatever they call themselves, over at Bedford. Movac seemed like they were only interested in bigger orders so Ketts it was. Dale that worked there was a top bloke but I think he left.
So it's mail order for me mostly now.

Don't know what the mastic stuff is like, I thought it might be thicker? Sounds like it's meant for chassis, where the normal epoxy is more all-rounder, sort of thing.
Think I'm all but out of epoxy otherwise I'd say nip over and grab some (i'm in Histon).

steveo3002 · Oct 20, 2009

right cheers for that ...im out towards haverhill so theyre a bit far anyway

hard to guess if the mastic has any kind of propertys suited to ropey old cars

spose just under £40 posted isnt too bad anyway

Chipper · Oct 20, 2009

If it's a one-stage jobbie that saves cost and faff, not having to overcoat.
Another place for normal epoxy is Colorite in Hanwell Middx, used to go there and they post too. Or paints4u.com do Lechler too.

steveo3002 · Oct 24, 2009

well ive ordered some..fingers crossed its decent stuff

any more comments welcome..always intrested

Ratty · Oct 24, 2009

In general, 2 pack epoxy adhesive (and I guess mastic falls into that category) will flow more but cure quicker if warmed and likewise will be thicker and cure more slowly if cool. The air temperature will therefore affect the cure time and you can speed the cure by applying gentle heat (like a hair-dryer) or retard it by keeping it cool.
Epoxies tend to last much longer than the given shelf life if kept in a cool dark place. If you go to use it in the future and it's gone a bit stiff in the tin then warming it will soften it (but make it cure quicker!).
:welder:

I'm not sure if this little bit of wisdom applies to epoxies but apparently polyester resins will cure in the bucket without any catalyst if exposed to UV light so best to keep the unused stuff well away from your welding area.
Also worth remembering for anyone using repair resin (glass fibre) or car body filler as these are all polyester resin products..keep well away from where you weld! :welder:

Chipper · Oct 24, 2009

We're talking about epoxy paint, the 2k variety, I think you're talking about a different sort of thing there... But its handy info!

Ratty · Oct 24, 2009

Chipper said:
We're talking about epoxy paint, the 2k variety, I think you're talking about a different sort of thing there... But its handy info!

You got me! :clapping:

Shoulda looked it up before I posted

. Still...s'not what I would call a mastic..that's my excuse an I'm sticking to it (no pun intended).

I've absolutely no experience of 2k epoxy paints but LOTS with epoxy resins, adhesives and.......mastics (the thick sticky flexible variety

)

Never mind...glad you think it handy info even if not for the item in question.

GeorgeB · Oct 24, 2009

Ratty said:
I've absolutely no experience of 2k epoxy paints but LOTS with epoxy resins, adhesives and.......mastics (the thick sticky flexible variety

I don't have any experience of epoxy which is badged as paint either but I can't help wondering if it's almost identical to epoxy adhesive and other epoxy mixes but thinned down a bit to make it seem more like paint and be a bit easier to apply. So I'm sure your observations are relevant.

I have epoxy resin and hardener which is sold primarily for making up fibreglass type structures as in boat building, etc. But I also use it like paint and it works a treat.

As for epoxy mastic, I can't really see the point. Perhaps a thicker coating will protect against stone chip damage, but epoxy is very strong in the first place. I would apply a thin coat of epoxy resin like a paint primer to bright or even slightly rusty steel on the underside of a car and would probably then cover that with conventional mastic, so it looked right and to protect the epoxy from UV damage, if not stone damage.

Ratty · Oct 24, 2009

I get what you're saying George and you might well be right in some instances but epoxies - like polyurethanes - are a HUGE family and one epoxy can have very different properties to another depending on what they are designed for. As an example, I use an epoxy casting resin which is so unlike anything I can buy in the UK - and believe me I have tested dozens that the companies would have me believe are similar - that I have to import it from the States. Actually I import two..a rigid and a flexible, which I then blend. Both have different catalysts and whilst the flexible catalyst will conveniently give a more rapid cure to the rigid resin, the catalyst from the rigid resin won't cure the flexible one at all.
I am all for finding cheaper ways to do things but in this instance I would go for the material that is designed for the job.

Smallfry · Aug 13, 2023

MG David said:
You might want to see the following thread:-

http://www.mig-welding.co.uk/forum/showthread.php?t=11190&highlight=epoxy+mastic

I went ahead and bought epoxy mastic and used it. So far so good. I will be able to give you a better answer in 10 year time!

Well, its now coming up to 14 years, so what's the verdict ?

bricol · Aug 13, 2023

Smallfry said:
Well, its now coming up to 14 years, so what's the verdict ?

Well, I'm still using the same Lancia I commented on in the linked thread - the rear subframe, the rear arches etc I had blasted in 2004/5 and used epoxy mastic on are still doing perfectly fine, currently only doing 150 mile a week commuting.

vw1 · Aug 13, 2023

I have used the rustbusters 121 epoxy mastic on the underside chassis of my vw. I used a paint bush and good enough for under the car. It's not uv stable and will chalk over time. For me I over coated with graveltex. I found it quite expensive buying in small quantities.

On my second vw project I brought jouton 80 winter grade and that allowed me to use under 15 degrees that was great for me as it was a winter project.

I have also used lechler but only on body panels and it sprays very nice and does sand well if needed.

Sean · Aug 13, 2023

Used Jotun too with a roller, went to use it again but its gone off in the tin...the fact "Boychild" borrowed it to paint a motorbike frame and line a tank last year i suspect its been cross contaminated.

norsa · Aug 13, 2023

Only one I've used Steve is the Jotun. Does a great job.
Nick

thinking of buying epoxy mastic..any others around?

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