# Two-component epoxy paints

Product-specific component ratios, induction and working life, preparation and film control, recoat versus service cure, and exposure limits for epoxy coating systems.

Reviewed: 2026-11-01

Tags: consumables, coatings, epoxies, 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](https://jotundatasheetsprod.blob.core.windows.net/ags/AG%C2%A416560%C2%A4Jotamastic%2090%C2%A4Euk%C2%A4GB.pdf)

## 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](https://jotundatasheetsprod.blob.core.windows.net/tds/TDS%C2%A416560%C2%A4Jotamastic%2090%C2%A4Eng%C2%A4US.pdf)

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](https://sgp.sika.com/content/dam/dms/sg01/b/sikagard_-62.pdf).

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](https://usa.sika.com/en/construction-products/coatings-water-repellents/chemical-resistant/sikagard-62.html).

**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](https://www.hempel.com/en-gb/api/Hempel/DataSheet/PDS/Download/15460/en-GB).

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](https://jotundatasheetsprod.blob.core.windows.net/ags/AG%C2%A416560%C2%A4Jotamastic%2090%C2%A4Euk%C2%A4GB.pdf)

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](https://sgp.sika.com/content/dam/dms/sg01/b/sikagard_-62.pdf); [Sika USA, substrate preparation](https://usa.sika.com/en/construction-products/coatings-water-repellents/chemical-resistant/sikagard-62.html).

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](https://jotundatasheetsprod.blob.core.windows.net/ags/AG%C2%A416560%C2%A4Jotamastic%2090%C2%A4Euk%C2%A4GB.pdf).

## Recoat readiness is not service cure

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

| Temperature | Pot life | Minimum recoat | Maximum recoat | Full cure |
| --- | --- | --- | --- | --- |
| 20°C | About 20 minutes | About 10 hours | About 2 days | About 10 days |
| 30°C | About 10 minutes | About 6 hours | About 1 day | About 5 days |

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](https://sgp.sika.com/content/dam/dms/sg01/b/sikagard_-62.pdf).

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](https://www.hempel.com/en-gb/api/Hempel/DataSheet/PDS/Download/15460/en-GB).

## 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](https://jotundatasheetsprod.blob.core.windows.net/tds/TDS%C2%A416560%C2%A4Jotamastic%2090%C2%A4Eng%C2%A4US.pdf).

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.