Epoxy Mastic

"It gave the best anti-corrosion results with no visible signs of rusting along the panel or the score mark - tough enough for a stand alone chassis coating" - OnTest Vedict in Practical Classics March 2007

Epoxy Mastic is a high build, high solids two pack (has a base and hardener) Epoxy paint coating for the renovation and protection of rusting and pitted steel exposed to severe environments. Epoxy Mastic can be applied successfully over wire brush cleaned steel and still offers the same exceptional performance as coatings applied over blast cleaned steel.

Epoxy Mastic will not flake, peel or blister - even under water. Resists oils, salt water and mechanical damage. Tough penetrating coating that is more flexible than the steel itself. Has six times the Epoxy Masticpenetration and adhesion of single pack products. Does not contain any harmful isocyanates.

So how does it work?
Epoxy Mastic is a two component Epoxy paint composed of nanoscale corrosion protective pigments in short chain molecules with very low surface tension.
This allows the paint to flow into all of the pits and troughs on the steel's surface, ensuring a tough penetrating primary bond.
This is the best kind of bond you can get with a paint finish.The high build epoxy forms a super strong protective barrier over the corrosion inhibiting pigments that hug the steels surface Excellent penetration and adhesion within a high build coating equals exceptional mechanical strength.

Why can't other paints do this?
Single pack paints (paint without hardener) used to protect steel against rust are the
Epoxy mastic colour chartmost common products. These products have standard sized pigments bound in long chain molecules and as such tend to lay over the pits and troughs on the steel's surface because of their high surface tension, the larger pigments are not able to collect to form a tight pigment matrix. This allows voids to form beneath the paint's surface,the thin film of the coating is not able to offer sufficient barrier protection over the high points on the steels profile, rust pockets form in the voids, the paint blisters and moves onto the next void and so on. The system flakes, peels and blisters.
This scenario cannot happen with Epoxy Mastic using a primary bond. They also tend to have less solid content. This means that the peaks on the steel's profile are soon exposed to the atmosphere and once again rust forms in the void and the system breaks down. Epoxy- Mastic's high solids content of 83% means that the finished dry film thickness is on average 30% thicker than the best single pack paints avail



What is the finish like?
Epoxy Mastic can be brush or spray applied like any other paint. It is supplied with Epoxy thinners to reduce viscosity when painting smaller components. It can be painted over or left alone.
It really is the complete answer, a high performance paint finish that has no equal it dries to an iron hard smooth finish see the pictures below of suspension components and engine bay coated with Epoxy Mastic Black.





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Epoxy Mastic



Technical Data Epoxy Mastic 121


Product description Epoxy Mastic 121  is a two-pack surface tolerant high solids epoxy mastic coating which is provided in 1 :1 mixing ratio for easy mixing and reduced wastage.

Epoxy Mastic 121 is applied by Spray brush or roller.

Recommended use

Anticorrosive coating for steel structures.

Epoxy Mastic 121  is suitable for areas with lower quality surface preparation and extended durability is expected.


Film thickness and spreading rate


Film thickness, dry (µm)100 – 400

Film thickness, wet (µm) 115 – 445

Theoretical spreading rate (m²/l) 8.7 – 2.9


Film thickness above is typical for what is achieved by one coat .          



Aluminium,  Black,  Buff,  Green,  Grey,  RedSolids (vol %)*72 ± 2 Aluminium75 ± 2 Black,  Buff,  Grey,  Green,  RedFlash point33ºC ± 2 (Setaflash)VOCAluminium

2,51 lbs/gal (300 gms/ltr) USA-EPA Method 24240 gms/ltr UK-PG6/23(97). Appendix 3Colours2,34 lbs/gal (280 gms/ltr) USA-EPA Method 24230 gms/ltr UK-PG6/23(97). Appendix 3


Gloss Level                  Semi gloss

Gloss retention  Fair

Water resistance           Very good

Abrasion resistance       Very good

Solvent resistance         Good

Chemical resistance      Good

Flexibility                      Good   *Measured according to ISO 3233:1998 (E)   


Surface preparation

All surfaces should be clean and free from contamination. The surface should be assessed and treated in accordance with ISO 8504.


Bare steelCleanliness: Power tool cleaning to min. St 2, mill scale free (ISO 8501-1:2007).  Improved surface treatment (blast cleaning to Sa 2½) will improve the performance. In case of hydrojetting the flash rust degree shall not exceed moderate in SSPC and NACE standards for water prepared surfaces.Shopprimed steelClean, dry and undamaged approved shopprimer.

Coated surfacesClean, dry and undamaged compatible primer. Contact Rustbuster office for more information. For maintenance UHPWJ to WJ2 (NACE No.5/SSPC-SP 12) or Power tool cleaning to min. St 2 for rusted areasOther surfacesThe coating may be used on other substrates. Please contact Rustbuster for more information.


Condition during application

The temperature of the substrate should be minimum 0°C and minimum 3°C above the dew point of the air.  The temperature and the relative humidity should be measured in the vicinity of the substrate. Good ventilation is usually required in confined areas to ensure proper drying. With forced ventilation, avoid heated air at first as this may cause surface drying and solvent entrapment. The coating should not be exposed to oil, chemicals or mechanical stress until fully cured.

Hydrojetting of steel surface makes a wet surface. The surrounding air must have a relative humidity not exceeding 85 %. Before painting the surface shall not be glossy with moisture, but can have a patchy apperance.


Application methods


SprayAirless 17 - 19 thou tip

Conventional spray thin up to 15% with No17 Epoxy thinners spray tip 1.5 - 1.9


Use a round brush. Care must be taken to achieve the spreading rate.


Use of a foam roller will provide the best hand finish results.


Application data

Mixing ratio (volume)1 parts by volume Comp. A (Base) to be mixed thoroughly with 1 part by volume , Epoxy Mastic 121 Comp. B (Curing agent).

MixingMix well and allow to stand (10 min. including mixing).Pot life (23°C)1½ hours

Thinner/ Epoxy Mastic 121 Thinner No. 17Note* The temperature of the mixture of base and curing agent is recommended to be at least 15°C, otherwise extra solvent may be required to obtain correct viscosity. * Too much solvent results in lower sag resistance and slower cure. * If extra solvent is necessary, this should be added after mixing of the two components.


Drying timeDrying times are generally related to air circulation, temperature, film thickness and number of coats, and will be affected correspondingly. The figures given in the table are typical with:*   Good ventilation (Outdoor exposure or free circulation of air)*   Typical film thickness*   One coat on top of inert substrate.



Temperature           Surface dry              Through dry                        Cured                           Dry to recoat min

5°C                               12 h                             20 h                                    d                  

10°C                               7 h                             14 h                                  14d                                   24h

23°C                               4 h                               7 h                                   7 d                                  10h

40°                                 2 h                               3 h                                   3 d                                    5h


Provided the surface is free from chalking and other contamination prior to application, there is normally no overcoating time limit. Best intercoat adhesion occurs, however, when the subsequent coat is applied before preceding coat has cured. If the coating has been exposed to direct sunlight for some time, special attention must be paid to surface cleaning and mattening/removal of the surface layer in order to obtain good adhesion.The given data must be considered as guidelines only. The actual drying time/times before recoating may be shorter or longer, depending on film thickness, ventilation, humidity, underlying paint system, requirement for early handling and mechanical strength etc.  A complete system can be described on a system sheet, where all parameters and special conditions could be included.



Handle with care. Stir well before use.

Packing size5 litres Comp. A (base) 5 litres Comp. B (curing agent) in 5 litre containers.


Health and safetyPlease observe the precautionary notices displayed on the container. Use under well ventilated conditions. Do not breathe or inhale mist. Avoid skin contact. Spillage on the skin should immediately be removed with suitable cleanser, soap and water. Eyes should be well flushed with water and medical attention sought immediately.For detailed information on the health and safety hazards and precautions for use of this product, we refer to the Material Safety Data Sheet.

DISCLAIMERThe information in this data sheet is given to the best of our knowledge based on laboratory testing and practical experience. However, as the product is often used under conditions beyond our control, we cannot guarantee anything but the quality of the product itself. We reserve the right to change the given data without notice.