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Corrosion Monitoring & Inspection Glossary - S

  • Sample: A small quantity of fluid that has been removed from the process stream for testing purposes.

  • Saturation: The degree of magnetization where a further increase in magnetic field strength produces a decrease in permeability of a material.

  • Scabs: See slivers.

  • SCC: Stress-corrosion cracking. Environmentally assisted cracking that can result when the combined action of stress, an electrochemical cracking environment, and temperature causes cracks to initiate and grow in a susceptible line-pipe steel.

  • Seam Weld: The longitudinal weld in pipe, which is made in the pipe mill.

  • Seam Weld Cracks: Cracks in the weld or weld zone of the longitudinal seam weld of the pipe.

  • Selective Corrosion Cracks: A localized corrosion attack along the bond line of electric resistance welds (ERW) and flash welds (FW), that leads to the development of a wedge shaped groove that is often filled with corrosion products.

  • Selective Pipe Replacements: Pipe replacements undertaken adjacent to critical areas such as dwellings.

  • Sensors: Devices that receive a response to a stimulus, e.g., an ultrasonic sensor detects ultrasound.

  • Sessile: Bacterial corrosion due to colonies formed on the surface. (See also Planktonic)

  • Shear wave analysis: see Ultrasonic thickness

  • Shielded Corrosion: Corrosion between the pipe and the protective coating, which is not controlled by cathodic protection currents. Commonly referred to as "cathodic shielding."

  • Side (Slip) Stream: A bypass loop or a direct outlet from the process stream. (Fluid may or may not be at the same velocity, temperature, and pressure as the main process stream).

  • Sizing: See characterization.

  • Slivers: A thin elongated anomaly caused when a piece of metal is rolled into the surface of the pipe. A sliver is usually metallurgically attached at only one end. In MFL inspections, a sliver is sometimes called a lamination.

  • Slug: Confined liquids within a gas pipeline. Smart Pig. See In-Line Inspection Tool.

  • Smart Pig: See In-Line Inspection Tool.

  • Sour Gas: Natural gas containing hydrogen sulfide in such proportion as to require treating in order to meet domestic sales gas specifications.

  • Sparger: Perforated pipe through which steam, air or water is sprayed.

  • Specified Minimum Yield Strength (SMYS): A required strength level that the measured yield strength of a pipe material must exceed, and which is a function of pipe grade. The measured yield strength is the tensile stress required to produce a total elongation of 0.5% of a gauge length as determined by an extensometer during a tensile test.

  • Sphere Pig: A spherical utility pig made of rubber or urethane. The sphere may be solid or hollow, filled with air or liquid. The most common use of sphere pigs is as a batching pig.

  • Stern-Geary constant: A polarisation resistance constant (B) used in determining a correction to the Tafel slope in conditions within 30 mV of the corrosion potential.

  • Strain: Increase in length of a material expressed on a unit length basis (e.g., inches per inch).

  • Strain Hardening: An increase in hardness and strength caused by plastic deformation at a temperature below the re-crystallization range.

  • Stress: Tensile or compressive force per unit area in the pipe wall as a result of the loads applied to the structure.

  • Stress corrosion cracking (SCC): Corrosion cracking produced synergistically by the combined influence of tensile stress and a corrosive environment. Synergistical

  • Stress Intensity Factor: A fracture mechanics term relating the crack size, geometry, and stress acting on a crack.

  • Stress Raiser or Concentration: A change in contour, discontinuity, gouge, or notch that causes local increases in the stress in a pipe.

  • Stress Relief: Reduction of residual stresses either through a mechanical overload or through an elevated temperature.

  • Stress Relieving (Thermal): Heating a metal to a suitable temperature, holding at that temperature long enough to reduce residual stresses, and then cooling slowly enough to minimize the development of new residual stresses.

  • Sub-Critical Crack: A crack that is not large enough to cause a failure of a pipeline at a given pressure.

  • Survey: Measurements, inspections, or observations intended to discover and identify events or conditions that indicate a departure from normal operation of the pipeline.

Corrosion Inspection and Monitoring