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MasterSeal P 681 Primer

MasterSeal P 681 Primer

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MasterSeal P 681 Primer (Formerly known as Mastertop P 681)

Two Component, Low Viscosity, Epoxy Based Primer

Solvent free, low viscosity, two component epoxy based primer used to protect steel and iron surfaces against corrosion.

For use with MasterSeal M860 & M861 Polyurea


MasterSeal M860 and M861 are hand applied, nonsolvented, 2-component, elastomeric polyurea coatings.

MasterSeal M860 is self-levelling.

MasterSeal M861 is thixotropic for applications to steeply sloping and vertical surfaces.


MasterSeal M860 and M861 are used in a variety of concrete waterproofing applications including roofing, balconies, terraces, podium decks, car park decks and water industry applications.

Two-part, hand-applied, rapid-curing, hydrophobic and chemically resistant polyurea waterproofing membrane

When you have essential waterproofing requirements or repairs and need to get facilities back into service as quickly as possible, a fast-track waterproofing membrane can save money. MasterSeal is a two-part, hand-applied, rapid-curing polyurea membrane that enables structures to be recommissioned with minimal downtime. It provides long lasting waterproofing with high elasticity for thermal movement. As a seamless coating (no joints or overlaps) there is no risk of leaky joints with excellent crack-bridging and chemical resistance. 

MasterSeal - Polyurea can be easily and seamlessly applied by brush, roller or squeegee.


  • Monolithic – no laps, welds or seams
  • Fully bonded
  • High water vapour permeability
  • Excellent mechanical properties
  • Excellent crack bridging capability
  • Resistant to puncture
  • Resistant to standing water
  • Mhermoset – does not soften at high temperatures
  • Remains elastic at low temperatures eg approx. - 45ºC
  • Non-solvented
  • ​Rapid curing: accepts light foot traffic after 4 hours at 20ºC
  • Hydrophobic material, so waterproofs the roof instantly
  • Highly elastic, can bridge cracks
  • Non-slip top coat available 
  • High tensile and tear strength, meaning the membrane remains durable where others tear

MasterSeal M860 Typically 1.35kg/m² per mm thickness. Minimum membrane thickness: 1.5mm.

MasterSeal M861 Typically 1.05 kg/m² per mm thickness. Minimum membrane thickness: 1.5mm

Application - Brief Guide (always refer to an up to date datasheet)

Surface Preparation:

The preparation of the substrate and the use of the appropriate primer are of paramount importance. All surfaces to which MasterSeal M 860 is applied should be sound, clean and dry and free from oil or grease, loose particles and any other substances which may impair adhesion. For substrate pre-treatment prior to the primer application see primer technical data sheet.

Concrete and cementitious screed

Concrete and other cementitious substrates must have a minimum pull off strength of 1.5N/mm². Any laitance present on the surface must be removed mechanically. Shot blasting is the preferred method. Release oil and other contaminants which may impair adhesion must be removed prior to the application of the primer.


In roofing applications, the asphalt should be cleaned by high pressure water jetting. In mechanically stressed applications the load bearing capacity of the asphalt should be suitable for the intended use and should be shot blasted so that at least 60% of the surface aggregate is ex-posed (min. quality e.g. AS-IC10). Blisters should be warmed, redressed and a de-bond tape applied over. Bituminous felts Blisters should be opened, dried out and repaired. Major cracks should be repaired and taped with de-bond tape.

Warning: MasterSeal M 860 will not bond to black APP modified bitumen felts nor is a suitable primer available.


All joints should be flush and taped prior to the application of the primer. All fittings must be flush with or sunk lower than the surface.

Iron and steel

Should be sand blasted to SA 2½ finish prior to application of the primer

  • Under MasterTop and MasterSeal systems, iron and steel surfaces (not appropriate for stainless steel surfaces).
    • Protects iron and steel against corrosion.
    • Ensures and high adherence on steel and iron surfaces.


    Other Primers

    Bitumen felt - MasterTop P 698

    Concrete cementitious / screed - MasterTop P 617 or MasterTop P 650

    Asphalt screed (mind. AS-IR10) - MasterSeal P 660 or MasterTop BC 375 N

    Plywood (preliminary tests are recommended) - MasterSeal P 660 or MasterTop P 691 GRP / GFK MasterTop P 691

    Iron and Steel - MasterTop P 681 Non-ferrous metals (e.g. aluminum, zinc) MasterTop P 684 Aged MasterSeal membrane MasterTop P 691