Jotamastic 90

Jotun Jotamastic 90 Overview

Jotun Jotamastic 90 is a premium surface-tolerant epoxy mastic coating designed for superior corrosion protection in harsh environments. It is part of Jotun's Jotamastic range, which is widely used in industries requiring long-lasting protection for steel structures, especially where surface preparation is challenging. The coating offers outstanding durability, excellent adhesion, and a smooth finish compared to traditional epoxy mastics.

Key Product Features

• Superior Corrosion Resistance – Long-term protection in aggressive marine, offshore, and industrial environments.
• Surface-Tolerant Technology – Adheres well to prepared surfaces, reducing time and costs.
• High Volume Solids (HVS) – Provides better coverage, lower VOC emissions, and reduced environmental impact.
• Fast Drying & Recoating – Allows for quicker turnaround times, minimizing downtime.
• Excellent Adhesion – Bonds effectively to steel, aged coatings, and other surfaces.
• Abrasion & Impact Resistance – Ensures long-lasting mechanical durability.
• Smooth Finish – Improves aesthetic appearance compared to rougher epoxy mastics.
• Versatile Application – Can be applied using airless spray, brush, or roller for various project needs.

Due to the extensive colour range it can be colour matched with the topcoat improving coverage

Jotamastic 90 is available in both Standard and Wintergrade options, depending on the environmental conditions.  Jotamastic 90 is also available in an aluminium version which provides extreme corrosion protection and exceptional water resistance.

The table below compares Jotun Jotamastic 90 to alternative but similar products.

Suitable Uses and Applications

Jotamastic 90 is surface tolerant and can be applied on surfaces that appear dry but where moisture remains and flash rusting has begun. It is ideal for use when blast cleaning is not possible.  It can be used on a variety of different substrates

• Carbon steel
• Galvanized steel
• Aged coatings
• Concrete

Jotamastic 90 is engineered for environments where long-term corrosion protection is crucial, including:

• Marine - Boat hulls, decks, and superstructures.
• Offshore - Oil platforms, pipelines, and steel structures in coastal environments.
• Industrial - Chemical plants, the exterior of storage tanks, power plants, and refineries.
• Infrastructure - Bridges, transmission towers, and steel structures in humid conditions.
• Maintenance & Repair - Excellent for refurbishment projects where full blasting isn’t feasible.

Basic Application Guide for Jotamastic 90

For detailed substrate specific instructions on how to apply Jotamastic 90 please see our application guide here

Step1 - Surface Preparation

• Best Practice - Abrasive blasting to Sa 2.5 (ISO 8501-1) for optimal performance.
• Minimum Requirement - Hand or power tool cleaning to St 2/St 3 (ISO 8501-1).
• Surface Condition - Must be dry and free of grease, oil, rust, and loose contaminants.

Step 2 - Mixing

• Whether using Standard or Winter grade Jotamastic 90, mix 3.5 parts Comp A to 1 part Comp B.

Step 3 - Thinning (usually not required)

• Thinning is usually not required but Jotun Thinners No.17 can be used if necessary

Step 4 - Applying Jotamastic 90

• Airless Spray - Recommended for large areas to ensure uniform thickness.
• Brush/Roller - Suitable for smaller areas or touch-ups; multiple coats may be needed.

Step 5 - Drying and Curing

• Please refer to the application guide for drying and curing times per grade of product and environmental conditions

Recommended topcoats that can be used with Jotamastic 90 include the Hardtop range, Jotatop Pro,  Conseal Touch-Up and Pioner Topcoat.

Frequently Asked Questions (FAQs)

The FAQ's below are for general guidance only.  For specific questions, please refer to the application guides on our product pages, or give us call and we will answer any questions that you have.

Q. What makes Jotamastic 90 different from standard epoxy coatings?

A. Unlike standard epoxy coatings, Jotamastic 90 is surface-tolerant, allowing application on hand prepared steel surfaces while maintaining strong adhesion and corrosion resistance.

Q. Can Jotamastic 90 be applied in cold temperatures?

A. Yes, but curing slows in lower temperatures. A winter-grade hardener can be used to speed up curing in cold conditions.

Q. Does Jotamastic 90 offer UV resistance?

A. As an epoxy-based product, it is not fully UV-resistant and may chalk over time. For enhanced UV resistance and aesthetics, a polyurethane topcoat such as Hardtop is recommended.

Q. What is the recommended surface preparation for best performance?

A. Abrasive blasting to Sa 2.5 (ISO 8501-1) is ideal. However, if blasting is not possible, power tool cleaning to St 2/St 3 can provide acceptable results.

Q. Can Jotamastic 90 be applied over old coatings?

A. Yes, provided the existing coatings are well-adhered, clean, and free from loose material.  Single pack type coatings must be well rubbed back.

Q. What is the maximum time before recoating?

A. Refer to the Jotamastic 90 Application Guide as this varies according to temperature and paint type. 

Q. Is Jotamastic 90 resistant to chemicals and solvents?

A. It offers excellent  resistance to water, and good resistance to oils and mild chemicals.  It is not suitable for prolonged exposure to strong acids or solvents.

Q. Can Jotamastic 90 be used underwater?

A. Yes, absolutely!  It is also suitable for splash zones.

Q. What is the best way to apply Jotamastic 90 for large projects?

A. Airless spray is the most efficient method for achieving an even, high-build coating.

Q. How does Jotamastic 90 compare to Jotamastic 87?

A. Jotamastic 90 offers a smoother finish, faster curing, and improved aesthetics while providing the same corrosion protection as Jotamastic 87.