As the world is awakening to a new green era, one of the world’s biggest inefficiencies is left unaddressed. It is estimated that 40% of all new steel is used to replace steel damaged or destroyed by corrosion—this equates to an estimated 3.2% of the world’s CO2 (carbon dioxide) emissions on maintenance alone.1
Within the oil and gas (O&G) industry, corrosion is known to be one of the main reasons for the failures of infrastructure.2 According to the Association for Materials Protection and Performance (AMPP), the annual cost of corrosion to the O&G industry in the U.S. alone is estimated at $27 billion, leading some to estimate the global annual cost of corrosion to the industry as exceeding $60 billion.4
Evidently, all metals are susceptible to corrosion, but the nature of crude oil itself promotes corrosion further due to its harmful impurities like napthenic acid and sulfur. The issue is further exacerbated within the industry as 90% of the materials used within the O&G network are metals.4 Therefore, the effective management of this natural phenomenon will not only save companies money but will also benefit the environment through saved resources and less repairing and replacing.
For decades, numerous key industries such as marine, automotive, and O&G have relied on hexavalent chromium [Cr(VI)] for protection against corrosion. Clearly, this chemical is highly effective in its objective of protecting metal assets; however, it is also known to cause cancer in humans and animals.6
Since being phased out, a popular alternative in the O&G industry has been zinc phosphate. Albeit somewhat effective, this inhibitor does not match the performance of chromate complexes. Additionally, despite extensive research conducted since the 1980s, Cr(VI) remains the benchmark corrosion preventative compound in most industries.3
A Highly Effective, Sustainable Inhibitor
Due to its micro-reservoir technology, a “new breed” of inhibitor is currently driving innovation in the protective coatings market. Manufactured by Hexigone Inhibitors Ltd. (Port Talbot, United Kingdom), Intelli-ion incorporates an active ingredient that has never been used effectively within coatings, making it a completely unique innovation.
The technology protects itself in a “smart” way via three modes of electrochemical protection. The active ingredient sits dormant in a micro-reservoir and is triggered “on-demand” when corrosion is sensed at the coating surface via ions or pH changes. Ions that pass through the coating are sequestered, rendering them neutral and also triggering the release of the inhibitor to migrate to the metal surface.
A defect in the coating or at a cut edge once under corrosive attack would have the same response from the reservoir system. The inhibitor forms a protective nano layer over the bare metal surface at the anode and cathode, forming insoluble salts with any dissolved metal ions preventing mass transport of corrosive ions as well as moderating under-film pH.
Independent Proof of Performance
Due to this unique approach, more than 40 coatings companies worldwide are formulating with Hexigone’s product—an outcome with exciting results in the protective, coil, and aerospace industries. Hexigone are currently formulating with a leading marine coatings manufacturer, Teal & Mackrill Ltd. (Teamac) (Kingston upon Hull, United Kingdom), who have demonstrated remarkable results when comparing performance against their current zinc phosphate inhibitor.
The top panel in Figure 1 was coated in a Teamac 2k epoxy primer containing Hexigone’s Intelli-ion AX1 and no zinc phosphate. By comparison, the bottom panel as coated in the same primer but contained zinc phosphate only. The samples were then scribed with a 1 mm (0.04 in) cutter and placed into the same salt spray changer in racks at an angle of 45°. The chamber was run in accordance with ASTM B117 continuous salt spray fog testing. This consisted of creating a fog of 5% w/v NaCI (sodium chloride) in distilled water at pH 7.0 at 35 °C (95 °F) consistently for 250 h.
Following the completion of 250 h of accelerated weathering (ASTM B117), the panels clearly showed superior corrosion protection with the 5% addition of Hexigone’s Intelli-ion AX1 inhibitor. The panel containing 29% zinc phosphate immediately peeled off, revealing extensive corrosion damage and no adhesion given the longer intact system. These results also showed that by using Intelli-ion, the weight percentage of required inhibitor is greatly reduced.
Furthermore, the Intelli-ion product range has been shown to be highly effective alongside more traditional inhibitors such as zinc phosphate, with performance jumping when the products are used in synergy. In Figure 2, Teamac added Intelli-ion and zinc phosphate to a 2 pk epoxy primer and compared it to their existing phosphate system. Following 750 h (ASTM B117), the company’s standard inhibitor was shown to be less effective than the new combination of Intelli-ion and zinc phosphate combined.
Between 1990 and 2012, 9,000 O&G pipeline failures due to internal corrosion were reported,4 accounting for 54.8% of all spills. With that taken into consideration, it is easy to see the real-world potential of these results, both financially and environmentally.
In one cost analysis with an O&G refinery, it was found that just one of their offsite chemical storage tanks cost $374,000 to repaint every 15 years due to corrosion. Hexigone’s AX1 has shown to increase metal asset longevity by 50% and can therefore increase the life cycle of the tank by seven years, halving the maintenance costs per tank.
In-depth Analysis via SVET, Natural Weathering
Further analysis of Hexigone’s product has recently been published in Surface Coatings International by University of Auckland researcher Sina Sheikholesami, who investigated the correlation between the scanning vibrating electrode technique (SVET) and natural weathering for analyzing corrosion. SVET is used to study localized corrosion behavior by giving spatially resolved corrosion measurements of microstructural changes in the material.
The results demonstrated that by using SVET, the industry can accurately understand how an inhibiting system is performing in 24 h, vs. nearly nine months of natural weathering.5
In this study, products A and B are Hexigone’s Intelli-ion technology, and product C is a market-leading chrome-free inhibitor. According to Sheikholesami, 5 the SVET maps show that the inhibitive species released at the cut edge by coating systems containing Intelli-ion were more efficient than the alternative chrome-free system.
This is visible via the red areas in Figure 3, which highlight high levels of anodic corrosion in product C following 24 h exposure in 5 wt. % NaCI solution.
Furthermore, these laboratory results correlated with natural weathering testing performed at the Muriwai Beach site in New Zealand. The three coated panel systems—A and B (Intelli-ion) and C (chrome-free alternative)—were assessed following 10 months of exposure according to the AS/NZS 2728 standard.
Figure 4 shows that product C has significantly more undercutting and corrosion than both of the Intelli-ion products, which supports the SVET analysis previously carried out.
Conclusions
In the O&G industry, it is vital to maintain the integrity of pipeline infrastructure to avoid economic and environmental disasters. Following the phasing out of Cr(VI), there was a clear need for innovation in order to offer the same level of protection against corrosion. Through pioneering micro-reservoir technology, Hexigone is able to incorporate chemicals that were previously incompatible with coatings and offer a smart inhibitor that delivers on price and performance.
Independent testing by coatings manufacturers and researchers have validated the performance of Hexigone’s Intelli-ion technology through industry standard testing such as ASTM B117, natural weathering, and SVET maps. These results clearly demonstrate that when used in a primer system, the additives dramatically increase corrosion protection, enabling coatings manufacturers to offer a differentiated product that results in reduced maintenance cycles and economic savings.
