Why you should use EM121 Epoxy Mastic under stone chip coatings

During day 3 of the Classic and Restoration Car Show 2022 at the NEC I met with Rob Marshall, Rob is. Freelance automotive journalist who’s articles you’ve likely read over the last 15 years.

Rob was at the show with his Triumph Dolomite removing the failing stone chip in the wheel arches and re-coating. Stone ship coatings are porous, and overtime will allow moisture to permeate the coating until reaching the surface the stone chip has been coated upon. If this surface is metal then you can be sure that our favourite four lettered friend will soon follow, RUST.

Luckily Rob is smarter than that and realised that a better base or primer product was needed, Rob chose EM121 Epoxy Mastic Oxide Red but why?

EM121 is a non-porous 2 pack modified epoxy mastic rustproofing paint suitable for steel, aluminium, galvanised metal and GRP. Being non-porous means that a liquid can’t pass through it, so whilst moisture could get through the stone chip it can’t get through the EM121 Epoxy Mastic.  For further details on EM121 please click here,

The image above hasn’t been scraped to remove the stone chip it’s simply failing and needs to be removed before further cleaning and re-coating.

After scraping away the stone chip you can now see the underlying condition of the EM121 Oxide Red in the arch. Now how long ago was the EM121 applied? 3 years, 5 years, 7 years well it’s 13 years old and still totally intact. Clearly attention was made to prepare the arches correctly prior to painting on the EM121 and this has really paid dividends.

When using coatings there are several very important things to remember,

  • Clean the surface thoroughly. Wash it with fresh water before anything else.
  • Preparation is king!! This will never change, better prep = better chance of coatings sticking.
  • Select the correct product for the job. Porous stone chip topcoat, non-porous EM121 basecoat. Inflexible topcoat (Raptor cough cough) flexible basecoat that won’t allow moisture through when the topcoat cracks EM121.

To assist you with your restoration projects this blog features a discount code that can be used for purchases of EM121 in all stocked colours online at www.rust.co.uk the code is DOLOMITE121

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