Hydrogen Sulfide Corrosion

Abstract

Hydrogen sulfide (H2S) corrosion poses significant challenges across various industrial processes, particularly in the oil and gas sector. Mild steel, commonly used in these applications due to its favorable cost and mechanical properties, is highly susceptible to corrosion when exposed to H2S. The electrochemical nature of this corrosion involves the aggressive dissociation products of H2S, leading to the formation of various iron sulfide scales.
Understanding the mechanisms of H2S corrosion is crucial for effective prevention strategies, which include cathodic protection, galvanization, and the use of chemical inhibitors. This article reviews the mechanisms behind H2S corrosion and outlines prevention methods employed in the industry.


Hydrogen sulfide corrosion and its prevention are critical considerations in many industrial processes, particularly in oil and gas operations. Mild steel, a prevalent structural material in this industry, is vulnerable to surface scale formation and the associated corrosive effects, necessitating specialized prevention methods.

The corrosion of steel in sulfide-containing solutions has garnered attention for its significance in industrial activities such as oil and gas production. This corrosion can lead to substantial economic losses and safety hazards in the petrochemical sector.

Mild steel's cost-effectiveness, mechanical strength, and corrosion resistance make it a preferred choice in the petroleum industry. However, the presence of pollutants, primarily sulfides, in oil can negatively impact the performance of mild steel.

H2S corrosion is primarily electrochemical. The dissociation products of H2S are aggressive and can catalyze electrochemical reactions, particularly the dissolution of iron.

Surface scale formation is a key factor influencing the corrosion rate. The kinetics of scale formation is crucial; unlike the straightforward iron carbonate precipitation seen in CO2 corrosion, H2S environments can produce several types of iron sulfides, including amorphous ferrous sulfide, mackinawite, cubic ferrous sulfide, and pyrite. Among these, mackinawite is typically the first to form on the steel surface through direct reactions.

The complex mechanisms of H2S corrosion complicate the quantification of iron sulfide scale formation kinetics. A proposed mechanism for iron dissolution in aqueous H2S solutions, based on the formation of a mackinawite film, is illustrated in Figure 1.



Figure 1: Proposed mechanism of H2S corrosion on Fe



Figure 2: Signs of hydrogen sulfide corrosion include shallow round pits with etched bottoms

Signs of hydrogen sulfide corrosion include shallow round pits with etched bottoms, indicative of the surface damage.

Methods of Hydrogen Sulfide Corrosion Prevention

1. Cathodic Protection: This technique reduces corrosion by making the material act as a cathode. A second material, more easily oxidized and acting as the anode, undergoes the majority of corrosion. For instance, zinc can be used as the sacrificial anode to protect an iron pipeline.

2. Galvanization: In this process, two different metals or alloys are placed in the same electrolyte. The metal with lower corrosion potential coats the material to be protected, acting as an anode and polarizing toward a higher potential. Conversely, the metal with higher corrosion potential acts as a cathode, polarizing toward a lower potential. Galvanization is a localized form of cathodic protection where the less corrosion-resistant material sacrifices itself to protect the stronger one.

3. Chemical Inhibitors: A highly effective prevention method involves adding chemical inhibitors like Catamin AB to fluids. In high concentrations of hydrogen sulfide, an iron sulfide layer forms on the material, with Catamin AB molecules stably adsorbing onto the surface. The vertically aligned molecules of Catamin AB create a monomolecular film that protects steel piping from dissolution and sulfide film growth.

Junee, 2014

Total Materia

Contáctanos
Resuelve tus desafíos de materiales.
Descubre cómo podemos ayudarte.