Currently viewing
Corrosion in the Oil Industry
The Final Report - FHWA-RD-01-156, 2001 - tabulates the following annual corrosion cost estimates relevant to the Oil and Gas Industry in the USA:
$7.0 Billion - Gas and Liquid Transmission Pipelines
$5.0 Billion - Gas Distribution
$3.7 Billion - Petroleum Refining
$1.4 Billion - Oil and Gas Exploration & Production
Every Sector of the Oil and Gas Industry is subject to significant corrosion-related costs. This applies to corrosion during production, transmission, and refining.

In addition to oxygen (O2) - both carbon dioxide (CO2) and hydrogen sulfide (H2S) are frequently associated with corrosion in the Oil and Gas Industry. Sulfur is not restricted to this Industry, but is often associated with it. Systems containing hydrogen sulfide (H2S) are generally referred to as "sour" - while those containing carbon dioxide (CO2) are usually termed "sweet".

Sour Corrosion - Hydrogen sulfide (H2S) in aqueous systems is known to be highly corrosive, dissociating to form acidic environments. An additional issue is the fact that it can react as a recombination "poison". As noted in the section on hydrogen damage, atomic hydrogen (H) is sufficiently small to penetrate into metals and alloys. By slowing the combination of hydrogen atoms on the metal surface to form hydrogen gas (H2), hydrogen sulfide (H2S) contributes to hydrogen damage. This brittle failure mode is often referred to as sulfide stress cracking (SSC).

Sulfide stress cracking (SSC) was first seen as a significant problem for the Oil and Gas Industry early in the 1950s. The failure mode is brittle cracking, and is observed in high-strength steels and welds. Sulfide stress cracking (SSC) is directly related to the amount of atomic hydrogen in the alloy.

Hydrogen sulfide gas (H2S) has an odor characteristic of "rotten eggs" at concentrations below 1.0 ppm (
parts per million). At much higher concentrations, the odor disappears - making it difficult for a person exposed to the gas to realize the danger.

Hydrogen sulfide gas (H2S) can rapidly result in death at concentrations above 600 ppm (parts per million). There have been a number of fatalities attributed to this gas. In one case, 22 fatalities and 320 hospitalizations were reported as the result of a malfunction in a flare designed to burn off excess gas at a sulfur recovery plant.

Sweet Corrosion - Carbon dioxide (CO2) can reduce the pH of aqueous systems so that they become more acidic through the formation of carbonic acid (H2CO3). Corrosion is often initially seen as metal dissolution - followed by pitting.

Pipelines - Corrosion is not the only cause of failures in pipelines, but it is one of the main causes. Pipelines can suffer from both external and internal corrosion. In general, pipelines will suffer from a form of localized corrosion (frequently pitting) rather than from general corrosion.

Microbiologically influenced corrosion (MIC) can also develop - either externally or internally. One of the most common microorganisms involved is the sulfate-reducing bacteria (SRB).

In the case of buried pipelines, the corrosivity of the soil can influence degradation. Factors that increase soil conductivity tend to increase corrosion. In addition, differences in local soil composition, aeration, moisture, etc. can produce differential cells that enhance corrosion.
 Currently viewing