The definitions of many of the corrosion-related terms used in this standard may be found in ASTM G193, which should be referenced for the most up-to-date definitions. Additional terms and selected definitions and abbreviations are highlighted below.
3.1
Acronyms used in this standard. The acronyms used in this standard are as follows:
a. A/C - Anode-to-cathode ratio b. AM - Additive manufacturing c. CC - Conversion coating d. CEA - Cognizant Engineering Authority e. CR - Corrosion rate f. Ecorr - Corrosion potential g. Egal - Galvanic corrosion potential h. EHC - Engineered hard chrome i. ESHE - Potential of standard hydrogen electrode j. HE - Hydrogen embrittlement k. HER - Hydrogen evolution reaction
l. HRC - Hardness Rockwell C m. Icorr - Corrosion current n. Igal - Galvanic corrosion current o. MIE - Metal-induced embrittlement p. mil - 1 mil is one thousandth of an inch (ie. 0.001 inch) q. NAWCAD - Naval Air Warfare Center – Aircraft Division r. OCP - Open circuit potential s. ORR - Oxygen reduction reaction t. pH - Power of hydrogen (pH = -log[H+]) u. PH - Precipitation hardening v. QA - Quality assurance w. QC - Quality control x. SCE - Standard calomel electrode y. T* - Tagnite z. UNS - Unified Numbering System aa. UTS - Ultimate tensile strength bb. ZRA - Zero resistance ammeter
3.2
Cognizant Engineering Authority (CEA). For the purpose of this standard, the Cognizant Engineering Authority is that entity from the procuring activity that provides, reviews, and approves any deviations from the technical requirements contained within this standard.
3.3
Corrosion. The Congressional definition of corrosion states that corrosion is "the deterioration of a material or its properties due to a reaction of that material with its chemical environment" and can be found in Title 10 U.S.C. §2228. It is inclusive of the deterioration of all materials, which can be caused through sun exposure, mold and mildew, wind, and other environmental elements. Some non-traditional examples include rotting of wood, degradation of concrete (carbonation, alkali-silica reaction phenomena), and degradation of composite materials due to reaction with the environment.
3.4
Corrosion rate. Material loss as a function of time due to corrosion. The corrosion rate in this standard is listed in units of mil/year and is used to determine the compatibility of a dissimilar, electrically conductive material pairing.
3.5
Dissimilar conductive materials. This standard defines conductive materials as dissimilar when two conductive materials are in contact or otherwise electrically connected to each other, in a conductive environment with the anodic member corroding at a rate greater than 0.009 mil/year.
3.6
Electrically conductive materials (conductive materials). For the purposes of this standard, an electrically conductive material is defined as any solid compound capable of carrying an electric current. This definition includes conductive carbon compounds and any other solid compound capable of undergoing galvanic corrosion.
3.7
Faying surface. Two or more surfaces joined, fitted closely, or tightly together.
3.8
Galvanic compatibility. Galvanic compatibility is defined as the maximum corrosion rate
(in mil/yr.), of the anodic member in a given galvanic couple, for which no protection against galvanic corrosion is required.
3.9
Galvanic corrosion. Galvanic corrosion manifests itself in the accelerated corrosion of the more active (anodic) conductive material of a dissimilar couple and decelerated corrosive effects on the less active (cathodic) conductive material. The rate at which the anodic member of the galvanic couple corrodes depends on the galvanic current of the coupled conductive materials, under the same environmental conditions.
3.10
Galvanic series. A galvanic series is a ranking of conductive materials and alloys based on their corrosion potential in a particular electrolyte solution or other environment. Conductive materials closely positioned in the series have electrical potentials nearer one another. As materials diverge in the series, the difference in potential grows. Table IV shows the galvanic series for conductive materials in an artificial seawater solution according to ASTM D1141, without heavy metals. The table provided is a reference and is not to be used for the determination of galvanic compatibility.