Abstract

Corrosive geothermal brines are a major challenge to geothermal power-plants. For cost reasons, plant designers prefer to use carbon and low alloyed steels, which are susceptible to uniform and localized corrosion when exposed to geothermal brines having acidic and saline properties. To solve such problem, coatings or inhibitors would be a protective solution as an alternative to the use of high alloyed materials.

This study investigated a coating system consisting of polyaniline/silicon dioxide based on resources locally available in Indonesia. Protection against corrosion of carbon steel was shown by long-term (28 day) exposure and electrochemical tests of coated carbon steels, performed in an artificial acidic and saline geothermal brine, comparable to the conditions encountered at a site in Indonesia.

Therefore, an integrated coating system is proposed for corrosion protection, combining the electrochemical functionality of polyaniline and the physical advantages of silica.

Introduction

Geothermal energy is a promising choice for alternative energy resources due to its reliability and low CO2 emissions1. One way to harness this energy, is to extract hot fluid from a geothermal well. Geothermal fluids are a complex medium with different physical and chemical properties depending on the location and depth of a geothermal well. Thus, these fluids can be corrosive to the geothermal power plant depending on the corrosivity class2, 3. The geothermal power plant consists of various parts, such as pipelines and heat exchangers. For continuous power generation, this power plant should be safe and durable. Therefore, it is important to protect the infrastructure in this environment from corrosion.

In terms of geothermal potential, Indonesia tops the list with nearly 29 GWe of energy savings4. Indonesia is located in the Ring of Fire and has unique geothermal resources, some of which are located in volcanic environments. This study focuses on the corrosion and corrosion protection of carbon steel in artificial geothermal water comparable to conditions in Sibayak, Indonesia. The Sibayak geothermal resource has a temperature range of 36 - 310°C, and the geothermal water is saline and acidic with pH 45. The combination of chemical composition and temperature-pressure condition can lead to corrosion on carbon steel6.

Keywords:
corrosion inhibition, pipeline corrosion, subsurface corrosion, renewable energy, ampp, exposure, permission, materials and corrosion, riser corrosion, corrosion management
Subjects:
Production Chemistry, Metallurgy and Biology, Pipelines, Flowlines and Risers, Non-Traditional Resources, Materials and corrosion, Geothermal resources, Well Integrity, Subsurface corrosion (tubing, casing, completion equipment, conductor), Corrosion inhibition and management (including H2S and CO2)
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