What special formula lets it withstand weeks-long salt spray testing with zero damage? Why does it beat all similar alternatives hands down?

Water-based systems generally suffer from weak corrosion resistance and poor resistance to water penetration. Enhancing the overall protective performance of coatings has become a core concern for numerous coating formulators.

Today we are proud to officially launch Imerys SteaShield™ 10W ultra-thin lamellar talc, hereinafter referred to as ST10W.

As a functional filler engineered for high-end coatings, it delivers outstanding barrier performance and features excellent compatibility with mainstream resin systems including waterborne acrylics.

It has achieved outstanding lab test results in three core indicators: salt spray resistance, water resistance as well as acid & alkali resistance, making it the preferred raw material for upgrading waterborne light-duty anticorrosive coatings

Part .01 Product Introduction

ST10W is a high-density ultra-thin lamellar talc developed and manufactured exclusively for high-performance protective coatings, antifouling coatings and anticorrosive coatings. Subjected to densification treatment, this talc features higher bulk density for outstanding transportation efficiency. Meanwhile, it generates minimal dust during application and delivers a superior construction experience.

ST10W boasts a whiteness value up to 91.0 with stable color performance, which will not interfere with the tinting effect of topcoats.

It has a specific surface area of 18.3 m²/g and a specific gravity of 2.78, coupled with a well-proportioned particle size distribution (D50 = 2.4 μm measured via the sedimentation method). The product disperses evenly within waterborne systems, effectively filling micro-pores inside coating films to form a dense protective barrier.

Composed mainly of silicon dioxide, magnesium oxide and other ingredients, ST10W features stable chemical properties and excellent compatibility with waterborne acrylic resins. It is applicable to a wide range of scenarios including primers, topcoats and rust-containing coating construction.

Part .02 Practical evaluation: Measurement of the protective performance of water-based systems

[1] Salt spray resistance [2] Water resistance [3] Acid and alkali resistance

salt spray resistance

This test was carried out based on a waterborne acrylic antirust coating system. Tinplate, a widely used substrate in the industry, was adopted as the base material. Different anticorrosive additives were blended for compound formulation. The whole testing process simulated actual construction and service environments, hence the test data is authentic and applicable for practical mass production.

{8% ST10W + 2% chromium-free silicate}

The dry film thickness of the primer was controlled at 75 μm. The coating film underwent air-drying at ambient temperature for 3 days before being placed into the salt spray chamber for a continuous two-week test. No obvious rust spots appeared throughout the test period, and the protective performance remained intact.

{8 wt% ST10W + 2 wt% chromium-free silicate + dispersant}

After optimizing the dispersion of the system under identical test conditions, a uniform coating film was obtained. No obvious rust spots, blistering or delamination were observed on the substrate following a two-week salt spray test.

{8 wt% ST10W + 2 wt% Zinc Phosphate LAZP045 + dispersant}

At a primer dry film thickness of 75 μm, the coating delivers outstanding stability under long-term salt spray exposure with remarkable synergistic anti-corrosion effects.

{Topcoat Application: Add 2% zinc phosphate together with 8% ST10W into the topcoat system.}

Dry film thickness of the topcoat shall be controlled at 40–50 μm. After long-term salt spray testing, the coating film remains intact with stable protective performance.

{rusted surface coating}

Rendering of Waterborne Acrylic Anti-Rust Coating System

Status from March 9 to June 2

Waterborne Acrylic Anti-rust Coating – Rust-over-Coating Effect

Status from March 9 to June 2

Cross-section diagram of waterborne acrylic anti-rust coating system (primer + topcoat).

The grey layer stands for primer while the blue layer is topcoat.

DFT of primer: 75 μm; DFT of topcoat: 40–50 μm

For common industrial rusted-surface painting working conditions, the 75 μm primer incorporated with ST10W can effectively restrain substrate corrosion after long-term placement. Even when the substrate carries slight inherent rust layers, this primer is capable of blocking rust propagation, meeting the light anti-corrosion requirements under complicated service conditions.

Salt spray corrosion is a major cause of metal substrate deterioration and a vital benchmark for judging anti-corrosion coating quality. With its special lamellar stacking structure, ST10W creates labyrinth barrier networks within the paint film. It effectively hinders salt and corrosive ion infiltration to the base material and greatly boosts the coating’s salt spray resistance performance.

Water resistance

Simultaneous water resistance test of Steashield 10W in 2K epoxy & 1K epoxy ester systems against blank specimens

Preparation ambient: 20 ℃, 70%RH

Process: Spraying | DFT: 50±5 μm | Flow time: 15 min | Bake: 70 ℃/30 min | Post-cure: 60 ℃×12 h

Samples with ST10W deliver obviously better water resistance than blank controls in both 1K and 2K epoxy ester systems.

Water-based coatings naturally suffer from water vapor infiltration issues. Prolonged immersion and high humidity commonly cause film whitening, poor adhesion, blisters and coating delamination. The layered sheet structure of ST10W seals off water molecule diffusion paths, densifies the coating matrix and greatly optimizes the overall water resistance of the coating system.

Acid and alkali resistance

Two-component epoxy system: conventional epoxy resin + amine curing agent.

Dosing of Steashield 10W: 3%, 5%, 7%, 10%, 15% calculated on mill base raw material weight.

Comparative tests were performed using zinc phosphate and aluminum phosphate as alternative fillers.

With 5% addition rate, zinc phosphate and aluminum phosphate of various grades show poorer acid resistance than 3% ST10W. Higher ST10W loading brings obvious enhancement in acid-resistant property.

Part .03

Verified by comprehensive testing, ST10W fits waterborne acrylic light anti-corrosion coatings perfectly. It applies to tinplate coating, hardware anti-rust protection, mild corrosion protection for regular steel structures and direct painting on rusted surfaces. Suitable for both primer and topcoat formulas, it works synergistically with silicate, zinc phosphate and other anti-corrosion fillers to boost comprehensive coating properties.

Thanks to its superior lamellar barrier structure, ST10W resolves the three major drawbacks of water-based anticorrosive coatings in one go: poor salt spray resistance, insufficient water resistance and weak corrosion resistance. Compared with ST10W-free formulas, it brings prominent performance gains during the test period. With good formula tolerance and convenient construction operation, ST10W provides comprehensive protection for coating films, being an optimal filler to upgrade the formula and overall quality of waterborne anti-corrosion paints.