Annoying problem!!

Annoying problem!!

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King Fisher

Original Poster:

739 posts

178 months

Tuesday 5th July 2011
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Hi chaps, Nick has a rather annoying problem with his S's chassis; he painted it with 2 coats of red oxide, which were then lightly sanded to give a nice rough surface for his top coat to bind to. Before he applied the top coat he wiped any dust off of the red oxide with a damp cloth, and allowed it to dry. He then applied a layer of Rustbuster Epoxy Mastic, under the assurance it was the bees knees. He mixed it as per the instructions, and painted it on. He applied two coats overall, but only applied the second once the first layer had started to harden. Now, when he jacks the car, the epoxy (and sometimes the red oxide) flake off. He now uses a soft pad on his jack, but what can he do to stop his chassis going rusty again? It's been waxoyled, but obviously the waxoyl comes off when the paint comes off!! Ideas would be excellent,

Thanks,

Tony

magpies

5,129 posts

181 months

Tuesday 5th July 2011
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Hi
I've made a similar blunder - shot blasted and repaired chass, painted 2 coats of white smoothrite then 'given' 2 coats of bitumen based coating which I was told will go hard, 2 weeks later I gave up and put another 2 coats of epoxy on top - it has gone hard but when knocked will flaje off both the epoxy and the bitumen to show the white smoothrite - damn annoying and bugga all I can do apart from touch up - at least the smoothrite is ok and so no bare metal showing
Mick



GreenV8S

30,152 posts

283 months

Tuesday 5th July 2011
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King Fisher said:
Now, when he jacks the car, the epoxy (and sometimes the red oxide) flake off.
That must be bitterly disappointing after all that hard work.

It might be interesting to see what state the epoxy is in that is coming off. Has it set properly and got reasonable strength? If not, I wonder whether it was mixed sufficiently with the right amount of hardener. (I haven't used that stuff you mention but I assume it uses some sort of hardener.)

If you think you have followed the instructions correctly I would contact the manufacturers customer support for advice.

In terms of minimising the damage, perhaps you could apply extra protection around the points you typically use to jack the car up? It's not as if there are all that many places that you _need_ to jack the car up by. For example a 1/4" rubber sheet stuck to the epoxy or wrapped and tied around it might spread the load enough to prevent damage. I have used vinyl floor covering to protect wishbones from A-frame chains in the past and it worked OK.

magpies

5,129 posts

181 months

Wednesday 6th July 2011
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GreenV8S said:
In terms of minimising the damage, perhaps you could apply extra protection around the points you typically use to jack the car up? It's not as if there are all that many places that you _need_ to jack the car up by. For example a 1/4" rubber sheet stuck to the epoxy or wrapped and tied around it might spread the load enough to prevent damage. I have used vinyl floor covering to protect wishbones from A-frame chains in the past and it worked OK.
/\ /\ This is what I am doing - the problem is the 'soft' coating, no matter what you put on top of it in the form of another coating, will crack the top coating because of the compression into the soft layer.

King Fisher

Original Poster:

739 posts

178 months

Wednesday 6th July 2011
quotequote all
Hi guys, thanks for the replies. Nick mixed it 50/50 hardener/paint, as per the instructions. You then let it stand, and then add thinners to it before painting it on. The red oxide holds up in most places, but even that can't stand a jack sometimes. Interestingly, on his trailing arms and wishbones he used red oxide followed by two coats of spray hammerite, which has proven to be immensely tough. Perhaps hammerite is the pain of choice afterall?

GreenV8S

30,152 posts

283 months

Wednesday 6th July 2011
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King Fisher said:
even that can't stand a jack sometimes.
If the paint has taken OK it should survive being jacked up with a wooden or rubber pad, but if you're picking it up by metal on metal you're pretty much guaranteed to wreck the paint.

Spathodus77

326 posts

208 months

Thursday 7th July 2011
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Hi,

I've used epoxy mastic on my drivers side outrigger and it has clung on fantastically well over the past two years with no chips or rusting showing through. I applied it direct to the bare metal as directed and I think I did two or three coats. I've also used it on the bonnet hinges and chassis cross member under the radiator and it is in fantastic shape in these areas too. I can't say the same for the passenger side outrigger which is painted with an alternative product.

These products are formulated to go onto bare metal so asking them to bond chemically to something else is probably the reason that some of them start flaking off.

Ralph

King Fisher

Original Poster:

739 posts

178 months

Thursday 7th July 2011
quotequote all
Spathodus77 said:
Hi,

I've used epoxy mastic on my drivers side outrigger and it has clung on fantastically well over the past two years with no chips or rusting showing through. I applied it direct to the bare metal as directed and I think I did two or three coats. I've also used it on the bonnet hinges and chassis cross member under the radiator and it is in fantastic shape in these areas too. I can't say the same for the passenger side outrigger which is painted with an alternative product.

These products are formulated to go onto bare metal so asking them to bond chemically to something else is probably the reason that some of them start flaking off.

Ralph
Hi Ralph,

The company actually state they can be used as a topcoat. This is what Nick did, and it has stuck fine in some places, but not in others.

Spathodus77

326 posts

208 months

Friday 8th July 2011
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Hi,

I checked through rustbusters website and technical datasheet. They only make reference to the point that this product can be painted onto steel. They do state that it can be overpainted but I think this means that you can put something else on top of the epoxy mastic not the epoxy mastic on top of something else.

If you have spoken to them they may have stated something different, and I have to admit that I have n't checked the info on the tin, but if I remember correctly the tins aren't particularly informative anyway.

Ralph

PS: In my previous post I stated that the bond between paint and metal is chemical, but I think 'physical' may be a better description.