Electrochemical properties of corroding mild steel (MS) surfaces were measured in real time using three closely spaced microelectrodes. Dissolved oxygen, pH, and ion currents were mapped simultaneously and noninvasively above a MS coupon partially coated with biopolymer gels. Calcium alginate (Ca-Alg [an extracellular biopolymer containing carboxylate functional groups]) and agarose (one without carboxylate functional groups) were tested. Corrosion occurred at approximately the same rate under the two biopolymer spots on the same coupon. Corrosion rates under these biopolymers were ≈ 4 mpy in a weak saline solution. Results suggested corrosion was not influenced by chemical properties of the biopolymer but possibly was controlled by oxygen reduction in noncoated regions of the coupon (i.e., a differential aeration cell).
Most soil quality measurements have been limited to laboratory-based
methods that suffer from time delay, high cost, intensive labor requirement,
discrete data collection, and tedious sample pretreatment. Real-time
continuous soil monitoring (RTCSM) possesses a great potential to
revolutionize field measurements by providing first-hand information
for continuously tracking variations of heterogeneous soil parameters
and diverse pollutants in a timely manner and thus enable constant
updates essential for system control and decision-making. Through
a systematic literature search and comprehensive analysis of state-of-the-art
RTCSM technologies, extensive discussion of their vital hurdles, and
sharing of our future perspectives, this critical review bridges the
knowledge gap of spatiotemporal uninterrupted soil monitoring and
soil management execution. First, the barriers for reliable RTCSM
data acquisition are elucidated by examining typical soil monitoring
techniques (e.g., electrochemical and spectroscopic sensors). Next,
the prevailing challenges of the RTCSM sensor network, data transmission,
data processing, and personalized data management are comprehensively
discussed. Furthermore, this review explores RTCSM data application
for updating diverse strategies including high-fidelity soil process
models, control methodologies, digital soil mapping, soil degradation,
food security, and climate change mitigation. Finally, the significance
of RTCSM implementation in agricultural and environmental fields is
underscored through illuminating future directions and perspectives
in this systematic review.
The distribution of pH near a metal surface indicates the positions of anodic (low pH) and cathodic sites (high pH). A microsensor, small enough that the pH sensing tip is confined to the diffusion layer, can be used to monitor pH near metal surfaces. This paper describes the mapping of pH near water-immersed mild steel surfaces using miniaturized iridium/iridium oxide pH microelectrodes in conjunction with a computer controlled micropositioner and data acquisition system. Two systems were analyzed: (1) a bare mild steel coupon exposed to artificial sea water, and (2) a mild steel coupon, first partially covered with the biopolymer, calcium alginate, and then exposed to artificial seawater. After 8 h exposure to seawater both coupons exhibited localized corrosion. On the coupon partially covered with calcium alginate gel, corrosion was limited to the area covered by biopolymer. On the bare coupon, corrosion was widespread. pH mapping of the coupons showed that low pH regions were identified with the corroded areas, and high pH regions with the uncorroded areas. These observations demonstrate that, in the abiotic environment, anodic sites on a mild steel surface can be fixed by partially covering the metal with biopolymer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.