Evaluation of the Protection Ability of a Magnesium Hydroxide Coating against the Bio-Corrosion of Concrete Sewer Pipes, by Using Short and Long Duration Accelerated Acid Spraying Tests.

Domna Merachtsaki,Eleftherios Anastasiou,Anastasios Zouboulis,Eirini-Chrysanthi Tsardaka

doi:10.3390/ma14174897

Domna Merachtsaki, Eleftherios Anastasiou + Show 2 more

Open Access

https://doi.org/10.3390/ma14174897

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Journal: Materials	Publication Date: Aug 28, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Aristotle University of Thessaloniki

Abstract

The Microbiologically Induced Corrosion (MIC) of concrete sewer pipes is a commonly known problem that can lead to the destruction of the system, creating multiple public health issues and the need for costly repair investments. The present study focuses on the development of a magnesium hydroxide coating, with optimized properties to protect concrete against MIC. The anti-corrosion properties of the respective coating were evaluated by using short and long duration accelerated sulfuric acid spraying tests. The coating presented satisfying adhesion ability, based on pull-off and Scanning Electron Microscopy (SEM) analysis measurements. The surface pH of the coated concrete was maintained at the alkaline region (i.e., >8.0) throughout the duration of all acid spraying tests. The consumption of the coating, due to the reaction (neutralization) with sulfuric acid, was confirmed by the respective mass and thickness measurements. The protection ability of this coating was also evaluated by recording the formation of gypsum (i.e., the main corrosion product of concrete) during the performed tests, by X-ray Diffraction (XRD) analysis and by the Attenuated Total Reflectance (ATR) measurements. Finally, a long duration acid spraying test was additionally used to evaluate the behavior of the coating, simulating better the conditions existing in a real sewer pipe, and the obtained results showed that this coating is capable of offering prolonged protection to the concrete substrate.

Highlights

The good operation and efficient protection of sewerage pipeline systems, especially against Microbiologically Induced Corrosion (MIC), is majorly important for urbanized societies
The magnesium hydroxide slurry was found to protect the concrete from MIC by effectively maintaining alkaline surface pH values and reacting with the sprayed sulfuric acid
The results of the present study indicated that the medium particle size of the raw magnesium hydroxide material used is optimal for the studied experimental conditions, in order to achieve adequate interacting ability with the sprayed sulfuric acid

Summary

Introduction

The good operation and efficient protection of sewerage pipeline systems, especially against MIC, is majorly important for urbanized societies. MIC is a specific type of corrosion mechanism that can take place usually in the larger diameter sewer pipes, constructed mainly from concrete, expected to highly affect the concrete and reduce the lifetime of the structure. This phenomenon has been widely studied during the last 100 years [1,2,3,4,5]. As a result the surface pH of concrete further lowers towards acidic values, until the development of Acidophilic Sulfur Oxidizing Bacteria (ASOB) at pH value 4 [10,11] The development of these microorganisms onto the inner concrete pipe surface can lead to the production of additional biogenic sulfuric acid. The concrete degrades further and the construction collapses, leading (among others) to major odor and pollution problems (e.g., leaking wastewater, polluting soil, etc.) [12,13]

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