Two-component epoxy paints

Jotun's Jotamastic 90 application guide gives 2 hours for standard grade and 45 minutes for winter grade at 23°C paint temperature. Pot life governs working time after mixing. Use the separate substrate-temperature, film-thickness and environment requirements for recoat and cure. Jotun, Jotamastic 90 AG, pp. 5–6

Identify the complete coating system

Jotamastic 90 is a polyamine-cured epoxy mastic with standard and winter grades. Specify product, hardener, substrate preparation, coating sequence, dry-film thickness and exposure together. Jotun, Jotamastic 90 TDS, issued April 13, 2026

Record the product code, region, base and hardener, and nominal dry film thickness (DFT).

Ratios: retain the units and the product identity

Mass and volume ratios are different instructions. The Singapore Sikagard-62 PDS, August 2026, version 06.02, specifies A:B = 3:1 by weight. It also lists different component densities. Weighing three parts of base and one part of hardener therefore does not mean measuring three equal-volume containers and one equal-volume container. Sika Singapore, Sikagard-62 PDS, pp. 1–2.

The US Sikagard-62 page instead specifies 1:1 by volume, with component premixing followed by three minutes of low-speed mixing. These are different regional instructions, not competing ways to measure one assumed universal formulation. Obtain the documents supplied for the actual kit. Do not borrow a ratio, thinner, pot life, or moisture allowance from a similarly named product sold elsewhere. Sika USA, Sikagard-62, mixing and application.

Bounded arithmetic: for the Singapore sheet's 3:1 mass ratio, a 4 kg combined batch contains 3 kg A and 1 kg B. This calculation illustrates the stated ratio; it does not establish that field splitting is permitted, that small batches can be measured accurately, or that either component can be substituted. Follow the supplier's batching and mixing instructions.

Induction, pot life, and temperature

Induction is a prescribed waiting period after mixing before application; pot life is the permitted working period of the mixed material under stated conditions. They are separate controls. Hempel's Hempadur 15460 PDS, October 2026, specifies 10 minutes induction at 20°C, increasing to 15 minutes at 15°C. Its spray pot life is 2 hours at 20°C and 3 hours at 15°C. Those values apply to the stated product and temperatures, not to epoxy paint generally. Read the supplier's timing convention rather than assuming that induction creates additional working time. Hempel, Hempadur 15460 PDS, p. 2.

Jotun’s November 27, 2024 guide bases pot life on paint temperature. If the supplier permits thinning, add thinner after the components are mixed. Jotun, Jotamastic 90 AG, pp. 5–6

As a practical interpretation, plan mixing, transfer, access, and application within the documented working period. Record the mixing time and actual material temperature. Do not use apparent fluidity alone as proof that a batch remains within specification.

Preparation and film control

The Singapore Sika sheet requires mechanically prepared, clean, dry concrete and specified abrasive blasting for steel. It prohibits moist substrates and requires 24-hour protection of fresh coating from damp, condensation, and water. That restriction differs from the US page's allowance for damp surfaces without standing water. Sika Singapore, substrate preparation and limitations; Sika USA, substrate preparation.

For Jotamastic 90, the application guide lists a typical 100–300 µm DFT per coat and 125–375 µm wet film thickness. It recommends wet-film measurement during application, followed by dry-film verification after hard drying. Ventilation supports drying and curing. These ranges belong to this product's specification; increasing thickness is not a universal way to improve protection. Jotun, application guide, pp. 6–7.

Recoat readiness is not service cure

The Singapore Sikagard-62 sheet provides this temperature-dependent example:

The sheet specifies approximately 0.2 mm per layer, with at least two layers recommended. The table shows why an apparently dry or recoatable film is not automatically ready for its final exposure. Sika Singapore, application information.

Hempadur 15460 separately reports touch dry, hard dry, and full cure at a stated 125 µm DFT. It requires surface roughening if its maximum overcoating interval is exceeded and a clean, dry surface before recoating. Its project specification takes precedence over generic table guidance. Hempel, drying and overcoating, p. 3.

Exposure, weathering, and handover

Jotun warns that epoxy finishes may chalk under sunlight and weathering. Its heat-resistance limits distinguish dry atmosphere, seawater, and crude-oil immersion, and distinguish protective properties from appearance. A dry-heat number therefore cannot establish hot chemical-immersion suitability. Obtain a compatible weather-resistant topcoat recommendation when color and gloss retention matter. Jotun, TDS, heat resistance, compatibility, and color variation.

For handover, connect the batch and component identities to the actual ratio, temperatures, mixing and application times, film measurements, recoat history, and exposure-release decision. Define chemical concentration, temperature, immersion or splash, and cleaning cycles with the supplier. Read the current SDS for both components and approved cleaning/thinning products. This engineering synthesis keeps a laboratory or datasheet claim attached to the conditions that make it meaningful.