Accelerated corrosion of marine-grade steel by a redox-active, cysteine-rich barnacle cement protein

Vinod K Murugan,Maja Budanovic,Arvind Latchou,Matteo Seita,Ali Miserez,Richard David Webster,Harini Mohanram

doi:10.1038/s41529-020-0124-z

Abstract

A serious consequence of marine biofouling on metallic structures is the insidious localized corrosion at the attachment sites of fouling organisms, such as barnacles. Albeit known, this phenomenon is poorly understood and currently mitigated using cost- and labor-intensive methods. In this work, we study the contribution to biofouling corrosion by a protein contained in the adhesive cement that barnacles secrete to attach to immersed substrates. We synthesize a specific cement protein of 20 kDa (CP20) from the barnacle Megabalanus rosa and study its corrosion behavior independently of the animal. Our results show that CP20 accelerates the corrosion rate of a marine-grade, mild steel from 0.7 to 1.6 mm year−1. Through chemical analysis of the corrosion products, protein adsorption studies on the metal surface, and cyclic voltammetry, we elucidate an intricate corrosion mechanism that relies on the strong adhesive properties of CP20 and its electrochemically active disulfide groups. Our results have far-reaching implications on the prediction and mitigation of biocorrosion in marine applications. Moreover, the protein-induced corrosion mechanism unveiled in our study may be extended to other scenarios to understand the degradation of metal alloys used in food storage and biomedical implants.

Highlights

Any structure that is submerged in seawater suffers from the colonization of microorganisms and macroorganisms—a phenomenon that is referred to as biofouling[1,2,3]
We find that recombinantly produced cement protein of 20 kDa (CP20) accelerates the corrosion rate of AH36 alloy—a mild steel commonly used in marine applications—up to 1.6 mm year−1, with visible pitting corrosion appearing just a few minutes after immersion of metal coupons in the protein-rich solution
Our experiments demonstrate that the high protein-induced corrosion (PIC) rate of CP20 stems from the combination of its strong adhesive properties and its propensity to oxidize iron (Fe), which results from the reduction of intramolecular disulfide bonds contained within CP20

Summary

INTRODUCTION

Any structure that is submerged in seawater suffers from the colonization of microorganisms and macroorganisms—a phenomenon that is referred to as biofouling[1,2,3]. This localized corrosion is difficult to detect and quantify. It may cause unexpected failure of subsea structures with serious environmental consequences[12,13]. Barnacles are capable of permanently attaching to immersed solid infrastructures by means of cement proteins that firmly fix the calcite base of the animal’s plate to foreign substrates[15]. Previous investigations of this type of biofouling have reported contrasting corrosion mechanisms. Because many other proteins contain similar redox-active moieties to those that govern CP20’s corrosion behavior, we believe that our findings may be extended to other applications—such as food storage and biomedical implants

RESULTS

DISCUSSION

METHODS