Chemical Treatment

A Closer Look at Microbiologically Influenced Corrosion

Microbiologically influenced corrosion (MIC) refers to corrosion caused by the presence and activities of microorganisms—microalgae, bacteria, and fungi. While microorganisms do not produce unique types of corrosion, they can accelerate corrosion reactions or shift corrosion mechanisms. Microbial action has been identified as a contributor to rapid corrosion of metals and alloys exposed to soils; seawater, distilled water, and freshwater; crude oil, hydrocarbon fuels, and process chemicals; and sewage. Many industries and infrastructure are affected by MIC, including oil production, power generation, transportation, and water and waste water.

Review of Applicable Indices for Evaluation of Water Quality

This article compares three water quality indices for the evaluation of water to be used in industrial processes in Iran. They include the Puckorious Saturation Index, Langelier Saturation Index, and Ryznar Stability Index. The most applicable index for use in that country is suggested.

Lead Contamination of Condensed Water

This article presents experimental data that show the solubility of lead in different waters. Specifically noted is the solubility of lead in condensed, or “pure,” water. It provides introductory information to those just entering the field of water corrosion and contamination as well as basic information to others not familiar with water corrosion and contamination.

Microbiologically Influenced Corrosion in a Copper Tube Chiller

The increased use of recycled water has led to the need for an effective water treatment program to prevent microbiologically influenced corrosion (MIC). This article describes an investigation of copper tubes in a chiller that failed from MIC because of a poor water treatment program.

Failure Analysis of a 30-in Subsea Oil Pipeline

This article presents the failure investigation of internal pitting corrosion on a 30-in (0.762-m) diameter subsea oil pipeline in western offshore India. Detailed laboratory and analytical studies were made on the failed sample to establish the cause and mechanism of failure. This article describes the analysis methodology, the probable corrosion and failure mechanism, and recommended preventive measures.

Failure Analysis: In-Situ Combustion Injector Well Tubing Failure

Severe plugging of in-situ combustion injector wells was found within 15 months of their commissioning in an on-land oil field in western India. Laboratory investigations were made to establish the cause and identify remedial measures. The tubing sections in the vicinity of the combustion front were exposed to an aggravated oxidation environment followed by moisture and oxygen intrusion through corrosion product. This triggered conversion of magnetite into porous, nonprotective hematite. The corrosion inhibitor treatment in the wet phase was found to be ineffective. A large amount of loosely bound corrosion product accumulated at the bottom of the hole during air/water injection. This plugged the well. Suitable well completion for the operating conditions was designed to prevent future failures.

Copper Pipe Failure by Microbiologically Influenced Corrosion

After a detailed investigation on the failure of copper water service pipes in a water distribution system, microbiologically influenced corrosion (MIC) was found to be the cause. Increased system disinfection appears to have remedied the problem. MIC is often overlooked in corrosion investigations of drinking water systems. This case history is a good example of telltale signs of MIC and the water environments in which this can occur.

Tuberculation Corrosion in Industrial Effluents

Tuberculation in waste water has long been a concern. Causes are an adverse mixture of water chemistry, construction materials, microbiological attack, and flow rate. Low velocity permits particulates and corrosion products to form deposits. Accumulated deposition leads to partial or complete blockage of pipelines, trapping of pigs, under deposit corrosion, and tuberculation. Tuberculation reduces flow rate. This article discusses tuberculation and presents a case study.

Caustic Treatment of Electric Utility Drum Boilers

Until recently, caustic water treatment was not used in high-pressure electric utility drum boilers in the United States because of concern over caustic gouging. Meanwhile, it was being used successfully in other countries. Many U.S. electric utilities have now converted their drum boilers to caustic treatment. This article describes the basics of caustic treatment and presents two case histories of successful use in the United States.

Measurement of a Corrosion Inhibitor Through Online Monitoring

Typical repair of reinforced concrete structures showing corrosion damage involves removal of carbonated or chloride-contaminated concrete and subsequent retrofilling with new concrete. Corrosion inhibitors that can be applied by spraying onto the concrete surface are an alternative. These products are relatively new and only limited long-term monitoring results are available. The combination of an inhibitor with monitoring of the corrosion behavior provides evidence of protection. This article describes long-term monitoring results of protected highway gallery columns in the Swiss Alps.

Evaluation of the Scale and Inhibition Effect of a Water Stabilizer

The complex effect of a water stabilizer on copper, iron, and zinc ions was tested by spectrophotometry, and its corrosion inhibition on copper alloy tubes was measured using electrochemical methods. The results showed that the water stabilizer not only had a strong antiscaling effect on Ca2+ and Mg2+, but also had certain complex effects on Cu2+ and Zn2+ under conventionally used concentration. The water stabilizer provided insufficient corrosion inhibition on copper tubes at the usual concentration.

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.

Special Considerations When Using Inhibitors

An inhibitor is a substance that slows down a chemical reaction (in the present context, a corrosion reaction). Corrosion inhibitors are commonly added in small amounts, either continuously or intermittently, to control serious corrosion in aggressive environments such as acids, cooling waters, and steam. While they can be highly effective, many inhibitors are also toxic, particularly in the concentrations suitable for shipping and storage. It is important to employ precautions to ensure personnel safety, environmental protection, and uninterrupted operation of equipment.

Corrosion by Water

The concentrations of various substances present in water in dissolved, colloidal, or suspended form are typically low but can vary considerably. The importance of these concentrations depends on the particular substance as well as the alloy, configuration, and function of the metallic structure with which the water comes into contact.