Atmospheric corrosion of low carbon steel in a coastal zone of Ecuador: anomalous behavior of chloride deposition versus distance from the sea

Atmospheric corrosion, especially in the coastal regions, has been a great problem in various structural components. In particular, low carbon steels are more susceptible to atmospheric corrosion due to favorable coastal climatic conditions. Generally, low carbon steels exhibit excellent mechanical strength making them preferable for use as reinforcement steel in concrete structures. As such, their atmospheric corrosion performance is a great concern amongst researchers. Despite several studies conducted in different climatic conditions, atmospheric corrosion of low carbon steels in coastal regions have not been fully explored. This should, however, take into consideration the influence of climatic factors on the corrosive behavior such as the relationship between the chloride deposition rate and the marine aerosol penetration.

Recently, different researchers have investigated the atmospheric corrosion of low carbon steels in different regions including Colombia, Ecuador, Chile, and Pakistan. Even though some good results have been obtained, various drawbacks have impeded the formulation of more accurate results. For instance, in different scenarios, accurate models for analyzing the influence of various factors such as the distance from the sea on the corrosion rate and chloride deposition rate have remained a challenge. Alternatively, in regions such as the Manabí province in Ecuador that has high construction potential, the existing structure has been built without taking into account the atmospheric corrosion protection knowledge, that is a key tool in deciding the corrosion protection criteria. This has led to less durable and low-quality structures. Prediction of corrosivity categories has been recently identified as an important aspect of studies involving the atmospheric corrosion of low carbon steels in coastal regions. From research and technical point of view, it has the potential of addressing the aforementioned drawbacks.

An international collaborative research among Professor Juan Carlos Guerra Mera (from the Technical University of Manabí), Professor Abel Castañeda Valdés (National Center for Scientific Research, Cuba), Professor Francisco Corvo (University of Campeche in Mexico) and Professor Juan José Howland (Technical University of Havana), and Dr. Joelis Rodríguez Hernández (Center of Research in Applied Chemistry in Mexico) investigated the atmospheric corrosion of low carbon steel exposed in coastal atmospheric condition. Specifically, the experiment was conducted in the coastal regions of Manabí province in Ecuador. The work is currently published in the journal, Materials and Corrosion.

Low carbon steels specimens were exposed at six different outdoor sites located at different distances from the sea. Corrosion by weight loss was evaluated for one year to classify the corrosion categories of the atmosphere concerning the low carbon steels. Based on the monthly chloride deposition rate, the environmental factors influencing the marine aerosol penetration and atmospheric corrosion rate were determined. Additionally, the authors also evaluated the monthly and annual changes in the corrosion rate and chloride deposition rate at different distances from the sea.

The research team noted that the deposition of the marine aerosol was anomalous with respect to the distance from the sea owing to the presence of estuary in the Manabí coastal region. Additionally, high chloride deposition rate, wind speed, temperature, and the coastal atmosphere were identified as the main factors influencing the marine aerosol penetration. For example, an increase in the wind speed and temperature highly influenced chloride deposition rate in the regions under shield conditions while a decrease in the RH-temperature complex exhibited significant influence in the zones without the shielded conditions. Therefore, both wet and dry periods showed almost equivalent corrosivity rate. In general, atmosphere high (C4) was identified as the predominant corrosivity category for approximately 20 years to come. The study will, therefore, provide the required knowledge such as corrosion protection measures required to build high-performance structures.