A Study on the Ozone-Resistive and Corrosion Protecting Method for Concrete Structure of Water Treatment Facilities by Applying Anti-Corrosive Arc Thermal Spraying Coatings

Abstract

There has recently been an increase in the introduction of advanced water purification facilities using ozone in order to effectively remove harmful substances that can not be removed by conventional water treatment methods due to the deterioration of water resources. However, ozone used in advanced water treatment facilities reacts with water to generate Hydroxy radical (OH-) with strong oxidizing power. This reaction causes deterioration of the internal waterproofing and anti-corrosion materials of the concrete structure for water treatment, which adversely affects the quality of the concrete. In order to solve this problem, a construction method using a stainless steel panel has recently been applied. In the stainless steel panel method, although the ozone resistance performance of the panel is excellent, it requires a high construction technique, expensive cost, and corrosion problem of the weld has occurred. Therefore, this study was to develop the method of concrete structure of water treatment facility with anti–corrosion and ozone resistance by applying metal spraying method which can easily manufacture metal panel as part of the development of finishing method to prevent deterioration of concrete structure of water treatment facility. And then it evaluated the applicability of anti-corrosion method for the concrete structure of advanced water treatment facilities in field. This paper is composed of 6 chapters in total as following.

Chapter 1, the background and necessity of the study and the purpose of this study are described. Chapter 2, the deterioration mechanism for domestic and international ozone, the recent trend of research, the current state of water treatment facility, and the method applied to each facility were examined and the limitations of the existing method were suggested. Chapter 3, the ozone resistance, chemical resistance, and electrochemical stability in acidic solution were evaluated by selecting the ozone-resistant sprayed metal for the application of the metal spraying for anti-corrosion coating. Chapter 4, the optimal surface treatment method was derived from the evaluation of ozone resistance and durability (ozone resistance and bond strength evaluation, water permeability, impact resistance) of the metal spraying coating. Chapter 5, the secondary ozone resistance, the durability test in the actual wastewater environment, the drinking water leaching performance evaluation, and the economic feasibility were examined for the field application of the metal spraying coating. Chapter 6, the conclusions of each chapter summarized and the comprehensive conclusions were obtained as followings.

1.Titanium (Ti) was selected as a spray metal through evaluation of ozone resistance, chemical resistance and electrochemical stability (corrosion potential: 291(mV), current density: 0.217(A/cm2), polarization resistance: 403.83 (k∙Ω∙cm2), corrosion rate: 4.07 (㎛/year))

2. The ozone resistance and the durability of the metal spray coating were evaluated and the optimum process and surface treatment method were derived. (Sand blast – Penetration type surface strengthening agent – Surface roughness agent – Metal spraying coating – Teflon-based sealing treatment)

3. The result in the field applicability evaluation of metal spray coatings showed no deterioration in the actual wastewater environment and satisfied the hygienic safety standards in the effluent performance of drinking water. Also, in the VE evaluation, the initial cost of metal spray coatings is higher than that of ozone-resistant paint, but it is very advantageous in terms of maintenance and is very advantageous in terms of initial construction cost and maintenance compared with stainless panel method.