Corrosion Basics

Corrosion Basics: Locating Pipeline Coating Defects with a Pearson Survey

One of the first successful techniques for locating coating defects (holidays) on buried pipelines using surface electrical measurements is the Pearson survey, named after its inventor.

Results Posted for NACE International’s 2016 Annual Corrosion Career Survey

Average annual salaries in 2016 are reported for corrosion professionals in the United States, Canada, United Kingdom, and Europe. A slight gain was seen for the United States and United Kingdom, while a larger increase was recorded in Canada.

Corrosion Basics: ICCP for Atmospherically Exposed Reinforced Concrete Structures

Impressed current anodes for atmospherically exposed steel in concrete are very different from anodes for underground and underwater applications.

Corrosion Basics: Stray Current Effects

Where stray currents discharge from a structure into the electrolyte environment in order to return to the source, corrosion will occur. If the corrosion is concentrated over a limited surface area, the integrity of the structure may be threatened in a relatively short period.

Corrosion Basics: Steam Generation in Power Plants

The greatest use of high-temperature water and steam is in electrical power generation. Historically, fossil fuels were used almost exclusively to heat water for steam until the introduction of nuclear power steam generators. This article briefly summarizes corrosion considerations for fossil fuel and nuclear fuel steam plants.

Corrosion Basics: Close-Interval Potential Surveys

The principle of a close-interval potential survey is to record the pipe-to-soil potential profile of a pipeline over its entire length by measuring potentials at intervals that do not significantly exceed the depth of the pipe.

Corrosion Management and the Significance of Regular Reporting

Regular inspection, monitoring, sampling, and chemical treatment activities are needed to mitigate corrosion. Data are not always adequately reported on a regular basis, however, which could gradually render an asset integrity management system less effective.

NACE International’s Annual Corrosion Career Survey Results for 2015

Corrosion professionals in North America and Europe have experienced another year of continued growth in career opportunities and salary levels, according to the 2015 Corrosion Career Survey conducted by Materials Performance magazine.

Wanted: Technical Articles for MP

To successfully communicate the wide variety of corrosion-related issues affecting corrosion professionals today, MP is actively encouraging corrosion control professionals worldwide to submit technical articles to share their corrosion-related experiences with over 36,000 NACE International members around the globe.

Intergranular Corrosion

Intergranular corrosion is a form of localized surface attack in which a narrow path is corroded out preferentially along the grain boundaries of a metal. It initiates on the surface and proceeds by local cell action in the immediate vicinity of a grain boundary. Although the detailed mechanism of intergranular corrosion varies with the metal system, its physical appearance at the microscopic level is quite similar for most systems.

Application of Organic Coatings

Organic coatings include latex paints, plastics, asphaltic materials, rubbers, and elastomers. The specific material selected for a coating job must have characteristics that would allow its proper application under all conditions existing during the coating process. Proper identification of the physical or other properties of the film expected from the application must be specified.

Water Constituents

The concentrations of various substances in water in dissolved, colloidal, or suspended form are typically low but can vary considerably. A hardness value of up to 400 ppm of calcium carbonate (CaCO3), for example, is sometimes tolerated in public supplies, whereas 1 ppm of dissolved iron would be unacceptable. In treated water for high-pressure boilers or where radiation effects are important, as in some nuclear reactors, impurities are measured in very small units such as parts per billion (ppb).

Steam Generation

The greatest use of high-temperature water and steam is in electrical power generation. Historically, fossil fuels (i.e., wood, coal, gas, and oil) were used almost exclusively to heat water and make steam until the introduction of nuclear power steam generators in the second part of the 20th century. The two types of power plants are different in many ways; however, they share a reliance on technically advanced water treatment and control for successful operation.

High-Temperature Corrosion by Sulfidation

The major constituent in flue-gas corrosion that differentiates it from common high-temperature atmospheric corrosion is the sulfur content. In general, oxidation by sulfur, or sulfidation, is a considerably more destructive form of high-temperature corrosion than oxidation by oxygen. Sulfide scales tend to crack and spall more readily than oxides, which can remain continuous and provide some degree of corrosion protection. In some cases, depending on the form in which sulfur is present in the atmosphere, continuous sulfide scales cannot form, so attack will proceed linearly; that is, the scale will afford no protection. The melting points of metallic sulfides usually are lower than those of the corresponding oxides.

Special Cathodic Protection Requirements for Specific Pipeline Applications

Most pipeline cathodic protection (CP) applications involve either galvanic anode or impressed current CP (ICCP) systems installed in earth for protection of external surfaces. Of the galvanic anode installations in neutral soils, magnesium is the most commonly used anode material. Rectifiers are the most common source of direct current power for impressed current systems.