1. Introduction

Anti-corrosion coatings represent the largest application segment of epoxy resins, accounting for approximately 35% of global epoxy resin consumption. In marine and offshore environments, steel structures face severe corrosion challenges from salt spray, humidity, UV radiation, and alternating wet-dry conditions. Epoxy anti-corrosion coatings, with their excellent adhesion, chemical resistance, and barrier properties, have become the primary protective system for offshore platforms, ships, port machinery, and coastal infrastructure. DENSON SEP series epoxy resin colorants provide stable coloring solutions for epoxy anti-corrosion coatings, ensuring color consistency and performance stability in harsh marine environments. This article presents three application cases of SEP epoxy resin colorants in anti-corrosion and marine coatings, analyzing their performance in zinc-rich primers, ballast tank coatings, and port machinery topcoats.

2. Technical Features and Mechanism

SEP epoxy resin colorants use epoxy resin as the carrier, ensuring excellent compatibility with epoxy anti-corrosion coating systems. Key technical features for anti-corrosion applications include:

Pigment weatherability: SEP colorants for anti-corrosion coatings primarily use inorganic pigments (iron oxide series, titanium dioxide, carbon black) with QUV 1000h ΔE ≤ 2.0, ensuring long-term color stability in outdoor marine environments.

Salt spray resistance: The pigment surface treatment technology prevents pigment particles from becoming corrosion initiation points. Neutral salt spray test (GB/T 1771-2007) shows that coatings with SEP colorants maintain no blistering or rusting after 1000 hours.

Chemical resistance: SEP colorants maintain stable performance in 5% H2SO4 and 5% NaOH immersion tests (7 days), with ΔE ≤ 2.0, meeting the requirements of ISO 12944 for C5-M high-corrosion environments.

Compatibility with zinc-rich primers: SEP colorants are compatible with high zinc content (80%+) epoxy zinc-rich primers, without affecting zinc particle activation and cathodic protection performance.

3. Application Case Study 1: Offshore Platform Steel Structure Epoxy Zinc-Rich Primer

An offshore oil platform project required epoxy zinc-rich primer with zinc content ≥ 80% (dry film), gray color (RAL 9006), and salt spray resistance ≥ 3000 hours. SEP series high-pigment carbon black colorant (Pigment Black 7) and titanium dioxide colorant (Pigment White 6) were selected at a 1:20 ratio to achieve the target gray color.

Test results: Dry film zinc content 83.2%, meeting the requirement; initial color L*=58.5, a*=0.2, b*=1.8, matching RAL 9006 standard (ΔE=0.8); neutral salt spray test 3500 hours without red rust, exceeding the 3000-hour requirement; adhesion (pull-off method) 8.5 MPa, meeting ISO 12944-6 requirements; cathodic protection current density 0.8 μA/cm², indicating effective zinc activation. Compared to traditional pigment powder addition, SEP colorants reduced mixing time by 40% and eliminated pigment dust pollution.

4. Application Case Study 2: Ship Ballast Tank Epoxy Anti-corrosion Coating

A bulk carrier ballast tank project required epoxy anti-corrosion coating with dark red color (for easy inspection), resistance to alternating seawater immersion and dry conditions, and a service life of 10 years. SEP series iron oxide red colorant (Pigment Red 101) was selected at 10% addition.

Test results: Initial color L*=38.2, a*=22.5, b*=12.8; after 1000 hours of alternating seawater immersion (40°C seawater 12h / 60°C drying 12h), ΔE=1.5, with no blistering or delamination; cathodic disbondment test (ISO 15711) disbondment radius 6.2 mm at -1.5V for 28 days, meeting the ≤ 8mm requirement; water vapor transmission rate 0.8 g/(m²·24h), providing excellent barrier protection. The dark red color facilitated visual inspection of coating integrity during tank inspections.

5. Application Case Study 3: Port Machinery Epoxy Topcoat

A port container crane project required epoxy topcoat with international orange color (RAL 2009) for high visibility, UV resistance, and 15-year service life in coastal environments. SEP series organic-inorganic hybrid colorant (iron oxide red + azo orange) was selected at 12% addition.

Test results: Initial color L*=45.8, a*=42.3, b*=38.5, matching RAL 2009 (ΔE=1.2); after QUV-A 2000 hours accelerated aging, ΔE=2.8, gloss retention rate 78%, meeting the 15-year durability requirement for C5-M environment; artificial weathering test (GB/T 1865-2009) 1500 hours without chalking (level 0) or cracking; impact resistance 50 kg·cm, flexibility 1mm, meeting the mechanical performance requirements for port machinery. The high-visibility orange color improved safety by making the crane structure easily visible during port operations.

6. Key Selection Parameters and Usage Recommendations

Pigment type: For anti-corrosion primers (zinc-rich, epoxy mastic), prioritize carbon black and titanium dioxide for neutral colors; for topcoats requiring vivid colors, use organic-inorganic hybrid pigments balancing color saturation and weatherability.

Color fastness: Select colorants with QUV 1000h ΔE ≤ 2.0 for C5-M marine environments; for C4 environments, ΔE ≤ 3.0 is acceptable.

Addition level: Primers 3%-8%, intermediate coats 5%-10%, topcoats 8%-15%; specific addition determined by target color depth and hiding power.

Compatibility testing: Verify compatibility with zinc dust, anti-corrosion pigments (zinc phosphate, aluminum tripolyphosphate), and fillers (talc, mica, barite) before mass production.

Construction parameters: Mix thoroughly before use; ensure substrate surface treatment reaches Sa 2.5 level (ISO 8501-1); apply at 5-35°C with relative humidity ≤ 85%.

7. Conclusion

DENSON SEP epoxy resin colorants demonstrate excellent performance in anti-corrosion and marine coating applications, providing stable coloring for offshore platform zinc-rich primers, ship ballast tank coatings, and port machinery topcoats. The three application cases confirm that SEP colorants meet strict requirements for salt spray resistance, cathodic disbondment, UV weatherability, and color fastness in C5-M high-corrosion marine environments. As global maritime and offshore engineering continues to develop, high-performance anti-corrosion coatings with stable color performance will play an increasingly important role. Dongguan DENSON Functional Materials Co., Ltd. will continue to optimize pigment surface treatment technology and anti-corrosion coating colorant systems, providing reliable coloring solutions for the marine anti-corrosion industry.