Prepping underside for painting

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Fri 17 Nov 2006 12:09
Prepping underside for painting - mss1tw
Just wanted to know what the best way to clean the underside prior to Hammeriting over any scrapes/patches where the underseal has come away would be? I was thinking of using Gunk but the only problem is of course it needs to be washed off leaving the underside wet.

I'll mainly be focussing on the sills/jacking areas.

Is painting straight over with normal silver Hammerite OK for the sills?

i'll probably use Hammerite underseal for the jacking areas/any other parts.

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Fri 17 Nov 2006 12:18
Prepping underside for painting - local yokel
I'd suggest a good pressure or steam wash when the weather look set to be dry for a couple of days. A good run will dry it out. Look out for a nice slow moving high pressure on the charts:

tinyurl.com/yfxell for weather charts up to a week out. No highs due wef Fri 17th.
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Fri 17 Nov 2006 12:32
Prepping underside for painting - oilrag
I would use waxoil with added engine oil brushed on with a wide brush.
Alternatively grease or just engine oil.
Renew every 6/12 months

If you really want a hard paint coating, best to get the underside steam cleaned.

But underneath, where the original coating is broken, the oil/grease solution will be more likely to prevent rust ( especially on an older car with existing rust) as it can creep into areas where you just cannot get an underseal that solidifies.
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Fri 17 Nov 2006 12:59
Prepping underside for painting - sierraman
I would concur with Oilrag,I have not been impressed with Hammerite or Tetrosyl,rust comes through quite quickly.Never use Tetrosyl on bare metal(like garages do after welding a patch) by the way.I would use a wire brush on an angle grinder to remove loose stuff,visor and welding gauntlets for protection,paint if you must ,then use Comma wax aerosol,better than Waxoyl IMO.It can be sprayed into chassis rails and box sections via drain holes.Re apply when the winter salt has washed it off,a good few months.Even rusty metal will stop rusting if it is completely covered in this stuff.
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Fri 17 Nov 2006 15:30
Prepping underside for painting - 659FBE
I also agree with the two comments above - wax based protection every time. In the real world of a vehicle underside being rusty, dirty and damp with seams, folds and welds, paint applied after build doesn't stand a chance.

The best product I have found was Supertrol (anyone know if it's still available?) with Waxoyl some way down the league table. Any wax based protection is best applied in the Summer after a hot spell. Leave the car and the tin of wax compound in the sun, so that there is minimum water present and maximum penetration due to the wax being thin.

659.
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Fri 17 Nov 2006 16:42
Prepping underside for painting - mss1tw
Cool thanks guys.
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