Multifunctional Inhibitor Mixtures for Abating Corrosion on HY80 Steel under Marine Environments

Abstract

The commercially available high strength steel, HY80, has been commonly used as part of naval hull construction since the 1950s. Corrosion of HY80 is associated with high costs due to material replacement, labour and lengthy down times of assets. The use of corrosion inhibitors as part of the steel paint system is a cost-effective method of stifling corrosion attack. Incorporation of an antimicrobial component into the inhibitor is also beneficial in combatting microbiologically influenced corrosion (MIC). This work examines the efficacy and mechanisms of corrosion inhibition from mixing lanthanum trans−4-hydroxy cinnamate (La(4OHCin) 3 ) with the candidate antimicrobial compounds, imidazolinium trans−4-hydroxy cinnamate (IMI-4OHCin) or cetrimonium nalidixate (CetNal) in artificial seawater. The most effective inhibitor combination was the mixture of La(4OHCin) 3 and IMI-4OHCin at their respective solubility limits (La+IMI). Examination of steel surfaces with optical profilometry after a 5 day immersion period concluded that the presence of La+IMI in solution resulted in significant minimisation of material corroded from the steel relative to the uninhibited sample. The inhibition mechanism for this mixture was determined to be predominantly anodic. On the other hand, all solutions containing the CetNal compound appeared to accelerate corrosion attack.

Multifunctional Inhibitor Mixture for Reducing Bacteria Growth and Corrosion on Marine Grade Steel

“…La+IMI, which showed the most effective abiotic inhibition from previous work, had almost no effect on the bacteria density, having less reduction in density compared to La(4OHCin)3 alone (Figure 2) (Catubig et al 2020). Thus, it too cannot combat both abiotic corrosion and MIC simultaneously.…”

“…In contrast, even at very small concentrations (< 100 µM), CetNal limited the bacteria density irrespective of the presence of La(4OHCin)3, demonstrating its effectiveness as an antimicrobial. Unfortunately, the mixture La+CetNal accelerated abiotic corrosion, as previously demonstrated, therefore it is not a viable option for this project (Catubig et al 2020). We present it here as an example of an efficient anti-microbial compound as compared with La(4OHCin)3, IMI-4OHCin and the La+IMI mixture.…”

“…The significant reductions in abiotic corrosion attack by the mixture La+IMI from our previous work and its potential surfactant properties made it the ideal system to investigate against MIC (Catubig et al 2020). The CetNal inhibitor was also included as it has been reported to have a strong effect on bacteria (Seter et al 2013) and will likely give a good anti-microbial baseline compared to the other inhibitors.…”

“…Cetrimonium nalidixate (CetNal) has previously demonstrated significant antimicrobial properties to single bacteria strains on coated mild steel in 0.01 M NaCl solution (Seter et al 2013). However, in artificial seawater all systems containing CetNal accelerated corrosion attack on HY80 steel (Catubig et al 2020).We include this compound in the current study to confirm the antimicrobial properties on a consortium of planktonic bacteria in addition to individual bacteria strains.…”

“…To effectively combat MIC, both microbial and abiotic corrosion effects need to be limited and we hypothesise that either a single, multifunctional inhibitor, or, more likely, a mixture of two inhibitors, is needed to eliminate bacteria growth and mitigate corrosion. Our previous work reported the mixture of lanthanum 4-hydroxycinnamate (La(4OHCin)3).and imidazolinium 4-hydroxycinnamate (IMI-4OHCin), referred to as La+IMI, provided more significant abiotic corrosion inhibition on the HY80 high strength steel in artificial seawater than La(4OHCin)3 tested separately (Catubig et al 2020).La(4OHCin)3 is known to inhibit corrosion to a similar level as sodium dichromate but at a quarter of the concentration, (Blin et al 2004).suggesting the La+IMI synergistically works together to provide a much more efficient corrosion inhibitor compared to sodium dichromate and La(4OHCin)3. In the current work, we exposed cultures of a single species of bacteria and a consortium of planktonic bacteria to the La+IMI mixture to verify the bactericidal properties of the inhibitors, in addition to their already confirmed abiotic corrosion properties.…”