MST Concrete Paint

MST Concrete Paint is a highly alkali-resistant paint developed for concrete, render and cement-based surfaces. It is formulated around the particular difficulties of mineral substrates.

Concrete and cement render are demanding substrates for paint, for two reasons. The first is alkalinity: cement hydration leaves a high pH at the surface, and binders that are not alkali-resistant break down chemically in that environment. This effect, known as saponification, makes the paint soften, become tacky and lose adhesion. The second is porosity: a concrete surface absorbs both water and paint, and where absorption is uneven the finish shows differences in sheen and colour.

This product is formulated against both problems. Its alkali-resistant binder resists saponification on mineral surfaces, while its filled structure evens out porosity and leaves a smooth, uniform finish. The result is both reliable adhesion and a surface free of patchiness and tonal variation.

Its second function is to protect. Unpainted concrete absorbs rainwater and airborne pollutants; in the freeze–thaw cycle the absorbed water expands and erodes the surface. The paint film limits that absorption, extending the life of the concrete surface and making it cleanable.

Typical applications include exterior fair-faced concrete and rendered surfaces, retaining and garden walls, basement and garage walls, block and aerated concrete surfaces, precast concrete elements, interior concrete and plastered walls, and plant room and warehouse walls.

The most common mistake is painting freshly poured concrete or new cement render too early. Cement hydration takes time; paint must not be applied until the surface pH has fallen and free moisture has left the substrate. Coating too early produces two problems at once: alkali attacks the binder in the paint, while moisture trying to escape lifts the film from beneath and blisters it. The waiting period varies with weather and element thickness; where there is doubt, check that the surface is dry before application.

The surface must be clean, dry, sound and free of dust. Friable and crumbling areas must be scraped back, and mould-oil residues removed with a suitable cleaner — where release oil is left, the paint will not bond. Laitance and any weak surface film must be removed mechanically.

Fill cracks and surface voids with suitable repair mortar and allow the repairs to cure. Clean off mould and algae staining, then rinse and dry the surface. On previously painted surfaces, remove blistered and loose layers and dull any sound remaining paint.

Absorbent new render and porous concrete must be primed. The primer does two jobs: it evens out absorption so the topcoat dries uniform in colour and sheen, and it binds a dusty surface to improve adhesion. Without primer, the first coat is drawn into the substrate, opacity falls, consumption rises, and patchiness caused by uneven absorption becomes permanent.

Apply by brush, roller or spray. Roller is preferred on large elevations, and the same method must be used across one surface so that no difference in texture appears.

The first coat may be thinned with a little water according to absorbency, which helps the paint work into the pores. The second coat is applied unthinned or barely thinned.

Work without interruption and keep a wet edge. Returning to a half-dried surface leaves dark bands at the laps, and those marks cannot be corrected once dry. On large elevations, finish work at natural break points such as corners, valleys or downpipes.

Do not apply to a hot surface in direct sunlight; the surface dries too early, the paint cannot penetrate the pores and adhesion suffers. Do not apply outdoors when rain is expected, or at low temperatures. Clean equipment with water.

The information below describes the general behaviour of masonry paints made for mineral substrates. For measured values specific to the product, refer to the technical data sheet (TDS).

Cement-based surfaces carry a high pH. Binders that are not alkali-resistant saponify and break down in that environment; the paint softens, becomes tacky and loses adhesion. An alkali-resistant binder withstands that reaction and delivers a durable film on mineral substrates.

The film limits absorption of rainwater and airborne pollutants into the concrete. That reduces surface erosion in the freeze–thaw cycle and makes the concrete surface cleanable. The breathable structure allows moisture beneath the surface to escape, preventing blistering.

Do not apply over concrete or render that has not fully cured. Surfaces under permanent water immersion, basement walls subject to hydrostatic pressure and industrial floors fall outside this product's scope; those conditions require waterproofing systems or epoxy floor coatings. Structural cracks cannot be bridged with paint and must be repaired with suitable material first.

Store in the closed original container in a cool, dry place. Being water-based, it must be protected from frost; do not use product that has frozen.