Results: A ‘New Breed’ of Corrosion Inhibitor for the Oil & Gas Industry
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 replaced steel damaged or destroyed by corrosion, this equates to an estimated 3.2% of the worlds CO2 emissions on maintenance alone. (C. Hoffmann, 2020)
Within the oil and gas industry, corrosion is known to be one to the main reasons for the failures of infrastructure (Kausalya Tamalmani, 2020). According to NACE International, the annual cost of corrosion to the oil and gas industry in the United States alone is estimated at $27 billion — leading some to estimate the global annual cost to the oil and gas industry as exceeding $60 billion. (Papavinasam, 2014)
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. Plus, the issue is exacerbated within the industry further as 90% of the materials used within the oil & gas network are metals. (Papavinasam, 2014) Therefore, the effective management of this natural phenomenon will not only save companies money but will also save the environment, through saved resources and less repairing and replacing.
For decades, numerous key industries such as marine, automotive and oil & gas have relied on hexavalent chromium [Cr(VI)] for protection against corrosion. This chemical is clearly highly effective in its objective of protecting metal assets, however, it is also known to cause cancer in humans and animals (United States Department of Labour, 2020)
Since being phased out, a popular alternative in the oil and gas industry has been zinc phosphate. Albeit somewhat effective, this inhibitor does not match the performance of chromate complexes; and despite extensive research since the 1980’s, hexavalent chromium remains the benchmark corrosion preventative compound in most industries (O Gharbi, 2018)
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. Hexigone Inhibitors’ ‘Intelli-ion®’ incorporates an active ingredient which has never been used effectively within coatings - making it a completely unique innovation.
The technology protects 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, and forms insoluble salts with any dissolved metal ions preventing mass transport of corrosive ions, as well as moderating under-film pH.
Independent proof of performance
Figure 1: results from marine paints manufacturer, Teamac, following 250 hours accelerated weathering (ASTM B117)
Figure 2: further results from marine paints manufacturer, Teamac, following 750 hours accelerated weathering (ASTM B117)
Due to this unique approach, over 40 coatings companies worldwide are formulating with Hexigone’s product – with exciting results in the protective, coil and aerospace industries. Hexigone are currently formulating with a leading marine coatings manufacturer, Teal & Mackrill Ltd (‘Teamac’), 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. The bottom panel was coated in the same primer but contained zinc phosphate only. The samples were then scribed with a 1mm cutter and placed into the salt spray chamber 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 NaCl in distilled water at pH 7.0 at 35°C consistently for 250 hours.
Following completion of 250 hours of accelerated weathering (ATSM B117) – the panels clearly show 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 show that by using Intelli-ion®, the weight percent of inhibitor required is greatly reduced.
Furthermore, the Intelli-ion® product range has been shown to work highly effectively 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 2pk epoxy primer and compared it to their existing zinc phosphate system. Following 750 hours ASTM B117, the company’s standard inhibitor was shown to be less effective than the new combination of Intelli-ion® and zinc phosphate combined.
When considering that between 1990 and 2012, 9000 oil and gas pipeline failures due to internal corrosion were reported (Papavinasam, 2014) - accounting for 54.8% of all spills - it 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 costs them $374,000 to repaint every 15 years due to corrosion. Hexigone’s AX1 has shown to increase metal asset longevity by c. 50% and can therefore increase the life-cycle of the tank by 7 years, halving the maintenance costs per tank.
In-depth analysis via SVET and natural weathering
Further analysis of Hexigone’s product has recently been published in Surface Coatings International by Aukland University Researcher, Sina Sheikholesami; who was investigating the correlation between the scanning vibrating electrode technique (SVET) and natural weathering for analyzing corrosion. SVET is used to study localised corrosion behaviour by giving a 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 hours, versus nearly 9 months natural weathering. (S. Sheikholeslami, 2020)
In this study, products A and B are Hexigone’s Intelli-ion® technology and product C is a market-leading chrome-free inhibitor. Sheikholeslami (2020) reported that 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 hours exposure in 5 wt. % NaCl solution.
Furthermore, these laboratory results correlated with natural weathering testing performed at Muriwai beach site in New Zealand. The three coated panel systems A, 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 the Intelli-ion® products, which supports the SVET analysis previously carried out.
Figure 3: SVET currency density maps of Intelli-ion (A and B) vs. market leading chrome-free inhibitor (C) after 24hours in 5 wt. % NaCl solution
Figure 4: Naturally exposed panels after 10 months of unwashed exposure on Muriwai beach, NZ.
Conclusion:
In the oil and gas industry, it is vital to maintain the integrity of pipeline infrastructure to avoid economic and environmental disasters. Following the phasing out of hexavalent chromium, 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 the corrosion protection, enabling coatings manufacturers to offer a differentiated product that results in reduced maintenance cycles and economic savings.
References:
C. Hoffmann, M. V. (2020, June 3rd). Decarbonization challenge for steel. Retrieved from McKingsey & Company: https://www.mckinsey.com/industries/metals-and-mining/our-insights/decarbonization-challenge-for-steel#
Kausalya Tamalmani, H. H. (2020). Review of Corrosion Inhibitors for Oil and Gas Corrosion Issues. Applied Sciences, 16.
O Gharbi, S. T. (2018). Chromate replacement: what does the future hold? Nature, 8.
Papavinasam, S. (2014). Corrosion Control in the Oil and Gas Industry. Houston, TX: Elsevier Inc.
S. Sheikholeslami, L. G. (2020). Evaluation of cut-edge corrosion in environmentally friendly waterborne coil-coatings using the Scanning Vibrating Electrode Technique (SVET). Surface Coatings International, 5.
United States Department of Labour. (2020, December 9th ). Hexavalent Chromium: Health Effects. Retrieved from United States Department of Labour: https://www.osha.gov/hexavalent-chromium/health-effects