In conjunction with Marine Energy Engineering Centre of Excellence (MEECE), Hexigone embarked on a rigorous real-world test of their anti-corrosion additive, Intelli-ion® AX1. From September 2022 to June 2023, 31 sets of panels were attached to a buoy. Deployed in a unique test location, they endured over 6000 hours, battling the formidable forces of the Celtic Sea.

The Test Setup: Panels and Preparation 

The panels used in this project were constructed from low carbon, cold-rolled steel featuring a matte finish. These panels are typically used in general-purpose sheet metal applications and adhere to ASTM A1008, A-109, and QQ-S-698 standards. 

To ensure a thorough evaluation, the panels were coated with various types of anticorrosion coatings: 

 Solventborne Alkyd  

Painted with a paintbrush:  

• 4 panels were painted with a co-blend of 3% AX1 & 2% Zinc Phosphate  

• 4 panels were painted with 5% AX1 only

Solventborne 2-Pak Epoxy 

Spray-painted with a compressed air paint gun: 

• 4 panels were painted with 0% AX1 

• 4 panels were painted with a co-blend of 5% AX1 & Zinc Phosphate  

All Solventborne 2-Pak Epoxy primers contained Zinc Phosphate anti-corrosive pigments, resulting in all epoxy-coated panels possessing a blend of anti-corrosive substances - for comparing co-blend panels against industry standards. 

Waterborne Acrylic 

• 8 panels were painted with a co-blend of 2% AX1 & 2% Polyphosphate 

These panels were also intentionally damaged. An 'X' was scribed into the coating to expose the bare metal using a 0.5mm Elcometer scratching tool, simulating damage to the paint system that can occur in real world applications. 

The Testing Rig: A Bespoke Solution 

To withstand the rigours of the Celtic Sea, a custom-designed test rack was engineered, by the skilled engineers at MEECE, to securely mount the panels onto the buoy. 

The panels were fixed flat against a drilled plastic backing board, held in place by plastic bolts, washers, and nuts with additional support from a holding strip at the bottom. This setup ensured the panels remained secure throughout the test duration, even under extreme weather conditions. 

Figure 1: Exploded assembly view of the basic panel mounting concept, for two adjacent panels.

Figure 2 and 3 below captured two key stages: the initial assembly of the panels onto the test rack, followed by the final installation of the test rack onto the buoy. 

Monitoring  

The panels were monitored over a period of nine months, with inspections at key intervals to assess damage and track the progression of corrosion.  

Installation Day - 21st September 2022

14th November 2022

Last Day - 8th June 2023 

The Results 

After 6000 gruelling hours of tirelessly battling the elements, it was time to recover the panels for analysis - the results were both surprising and promising.  

Solventborne Alkyd - 6000 Hours of Live Coastal Testing

The results from both formulations are strikingly similar, demonstrating high performance for both the co-blend of 3% AX1 and 2% Zinc Phosphate (left) and the AX1-only formulation (right). When stripped with solvent, their performance remains consistently high and a like with corrosion localised at the scribe line and minimal overall. The full metal substrate beneath the coating remains fully protected, highlighting the effectiveness of the anti-corrosive formulation.

Solventborne 2-Pak Epoxy - 6000 Hours of Live Coastal Testing

Formulated with a 5% addition of AX1, the panels on the (right) clearly showcase enhanced durability and coating adhesion compared to the panels on the (left), with 0% AX1. Despite being coated with alternative anti-corrosive pigments, the (left) panels show significant degradation - nearly completely destroyed.

Waterborne Acrylic  - 6000 Hours of Live Coastal Testing

The waterborne acrylic panels have demonstrated remarkable performance under real-world conditions - showing consistent results across all panels even after being stripped with solvent to reveal the underlying results. Notably, only the primer contained AX1; the topcoat did not.

Among all the results, the performance of the waterborne acrylic panels is particularly noteworthy - exceeding expectations and even surpassing the solventborne 2-pak epoxy coatings in real-world conditions. 

Even after stripping both sets of panels with solvent to reveal the underlying results, the contrast remains striking – the waterborne acrylic panels containing AX1 dramatically outperform the solventborne 2-pak epoxy panels.  

The Waterborne Acrylic formulation was developed in collaboration with Xyntra. 

David Graham, the Managing Director of Xyntra commented:  

"We are highly impressed with the performance of AX1 and have been collaborating closely with Hexigone to design a polymer system that leverages its capabilities in a water-based application. The results so far have been very encouraging." 

Adhesion - 6000 Hours of Live Coastal Testing

The addition of AX1 also significantly improved the adhesion of the waterborne acrylic paint system. During the pull-off test, only the topcoat could be removed, while the primer layer remained firmly fastened to the metal substrate. The dolly’s were removed at 450 psi and 300 psi. 

Conclusion 

The outcomes of this investigation have provided Hexigone with valuable, actionable insights. The buoy panels endured over 6,000 hours of coastal testing, offering a true assessment of the paint systems' ability to withstand harsh environmental conditions. 

As expected, the panels treated with Intelli-ion® AX1 demonstrated a significant improvement in corrosion resistance compared to those without AX1. However, the most unexpected finding was the exceptional performance of the waterborne acrylic panels. 

With the industry increasingly shifting towards more sustainable solutions, and away from those that include volatile organic compounds (VOCs) and other health-hazardous chemicals, the demand for waterborne acrylic coatings is rapidly growing. Based on these findings, Intelli-ion® AX1 has the potential to accelerate the broader adoption of waterborne acrylic coatings in marine applications.