Corrosion Terminology - S's

sacking—scrubbing a mixture of a cement mortar over the concrete surface using a cement sack, gunnysack, or sponge rubber float.

sacrificial anode—see galvanic anode.

sacrificial pigment—a pigment that provides cathodic protection to the substrate by galvanic action[contrast with corrosion-inhibitive pigment].

sacrificial protection—reduction of corrosion of a metal in an electrolyte by electrically connecting the metal to a galvanic anode (a form of cathodic protection).

sag—nonuniform downward flow of a wet-applied coating under the force of gravity that results in an uneven coating having a thick lower edge.

sample—portion of material taken from a larger quantity in a manner intended to be representative of the whole, typically used for test purposes.

scaling(1) the formation at high temperatures of thick corrosion-product layers on a metal surface. (2) the deposition of water-insoluble constituents on a metal surface.

scanning electron microscope—an electron optical device that scans a beam of electrons across a surface and collects the resulting electrons or photons to form an image whose contrast is determined by topography, elemental composition, or other properties.

season cracking—(an obsolete term) a form of environmental cracking of brass in the atmosphere.

selective dissolution—see dealloying .

selective leaching—see dealloying.

sensitization—a metallurgical state caused by certain heating, cooling, or cold working conditions that results in precipitation of constituents (e.g., carbides in a stainless steel) at grain boundaries, thereby causing an alloy to be susceptible to intergranular corrosion or intergranular stress corrosion cracking in a specific environment in which the alloy would normally exhibit corrosion resistance.

sensitizing heat treatment—a heat treatment that produces sensitization.

shallow groundbed—one or more anodes installed either vertically or horizontally at a nominal depth of less than 15 m (50 ft) for the purpose of supplying cathodic protection current.

shelf life—the maximum length of time packaged materials (e.g., coating materials) can be stored, at specified conditions, and remain in usable condition.

shielding(1) protecting; protective cover against mechanical damage. (2) preventing or diverting cathodic protection current from its natural path.

shop coat—one or more coats applied in a shop or plant prior to shipment to the site of erection or fabrication.

shot blasting—abrasive blast cleaning using metallic (usually steel) shot as the abrasive.

shot peening—inducing compressive stresses in the surface layer of a material by bombarding it with a selected medium (usually steel shot) under controlled conditions.

sigma phase—an extremely brittle Fe-Cr phase that can form at elevated temperatures in Fe-Cr,Fe-Cr-Ni and Ni-Cr-Fe alloys.

slip—a deformation process involving shear motion of a specific set of crystallographic planes.

slow strain rate technique—an experimental technique for evaluating susceptibility to environmental cracking. It involves pulling the specimen to failure in uniaxial tension at a controlled slow strain rate while the specimen is in the test environment and examining the specimen for evidence of environmental cracking.

slushing compound—oil or grease coatings used to provide temporary protection against atmospheric corrosion.

solid solution—single crystalline phase containing two or more elements.

solution heat treatment—heating a metal to a suitable temperature and holding at that temperature long enough for one or more constituents to enter into solid solution, then cooling rapidly enough to retain the constituents in solution.

solvent cleaning—removal of oil, grease, dirt, soil, salts, and contaminants using organic solvents orother cleaners such as vapor, alkali, emulsion, or steam. [See SSPC-SP 1.]

spalling—the spontaneous chipping, fragmentation, or separation of a surface or surface coating.

spark test—a high-voltage electrical test in which a spark is used to detect a discontinuity in a coating.

specular gloss—reflection of light, as from a mirror, as opposed to diffuse reflection in all directions.

splash zone—the portion of a marine structure that is intermittently wetted by waves,wind-blown water spray, and tidal action. (Surfaces that are wetted only during major storms are not included.)

specimen—prepared portion of a sample or coupon upon which a test is intended to be performed.[also known as test specimen.]

spreading rate—the average area covered by a unit volume of coating material at a specified dry film thickness.  (Spreading rate is usually specified as square meters per liter or square feet per gallon.)

stainles ssteel—steel containing 10.5 mass percent or more chromium, possibly with other elements added to secure special properties.

standard electrode potential—the reversible potential for an electrode process when all products and reactants are at unit activity reported on the standard hydrogen electrode scale.

standard jetting water—water of sufficient purity and quality that does not impose additional contaminants on the surface being cleaned and does not contain sediments or other impurities that are destructive to the proper functioning of water jetting equipment.

steel—a material that has more iron, by mass percent, than any other element and contains carbon generally less than 2.1 mass percent.

steel shot—small particles of steel with spherical shape that are commonly used as an abrasive in abrasive blast cleaning or as a selected medium for shot peening.

step potential—the potential difference between two points on the earth’s surface separated by a distance of one human step, which is defined as one meter, determined in the direction of maximum potential gradient.

stepwise cracking—see hydrogen-induced cracking.

stray current—current flowing through paths other than the intended circuit.

stray-current corrosion—corrosion resulting from stray current.

stress corrosion cracking—cracking of a material produced by the combined action of corrosion and sustained tensile stress (residual or applied). [See environmental cracking.]

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.

structure-to-electrolyte potential—the potential difference between the surface of a buried or submerged metallic structure and the electrolyte that is measured with reference to an electrode in contact with the electrolyte.

structure-to-soil potential—see structure-to-electrolyte potential.

structure-to-structure potential—the potential difference between metallic structures, or sections of the same structure, in a common electrolyte.

submerged zone—the surface area of a marine structure that is always covered with water and extends downward from the splash zone and includes that portion of the structure below the mud line.

subsurface corrosion—see internal oxidation.

sulfidation—the reaction of a metal or alloy with a sulfur-containing species to produce a sulfur compound that forms on or beneath the surface of the metal or alloy.

sulfide stress cracking—cracking of a metal under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide (a form of hydrogen stress cracking).

surfacepotential gradient—change in the potential on the surface of the ground withrespect to distance.

surfaceprofile—theirregular peak and valley profile on a bare surface that can result fromoperations such as abrasive blast cleaning or power tool cleaning. [also calledanchor pattern]

sweep blast cleaned surface—See brush-off blast cleaned surface.