Exfoliation is a structure-dependent form of localized intergranular corrosion that follows grain boundaries in the rolling direction of wrought materials, particularly aluminum alloys. Highly cold-worked materials with elongated grain boundaries tend to be most affected. The article provides information on accelerated salt spray and total-immersion testing methods to help rate the exfoliation corrosion susceptibility of various aluminum alloys and alloy compositions. It also discusses visual assessment challenges and identifies several ASTM designations and where and how they apply.

This article describes the commonly observed forms of airplane corrosion, namely: general corrosion, exfoliation corrosion, pitting corrosion, microbiologically induced corrosion, galvanic corrosion, filiform corrosion, crevice corrosion, stress-corrosion cracking, and fretting. It discusses the factors influencing airplane corrosion from the manufacturing perspective: design, manufacturing, and service-related factors. The article explains the collection of corrosion data and provides an overview of the implementation and evolution of airline corrosion prevention and control programs and directions being considered in the design for corrosion prevention of airplanes.

This article focuses on the various forms of corrosion that occur in the passive range of aluminum and its alloys. It discusses pitting corrosion, galvanic corrosion, deposition corrosion, intergranular corrosion, stress-corrosion cracking, exfoliation corrosion, corrosion fatigue, erosion-corrosion, atmospheric corrosion, filiform corrosion, and corrosion in water and soils. The article describes the effects of composition, microstructure, stress-intensity factor, and nonmetallic building materials on the corrosion behavior of aluminum and its alloys. It also provides information on the corrosion resistance of anodized aluminum in contact with foods, pharmaceuticals, and chemicals.

Corrosion, fatigue, and their synergistic interactions are among the principal causes of damage to aircraft structures. This article describes aircraft corrosion fatigue assessment in the context of different approaches used to manage aircraft structural integrity, schedule aircraft inspection intervals, and perform repair and maintenance of aircraft in service. It illustrates the types of corrosive attack observed in aircraft structures, including uniform, galvanic, pitting, filiform, fretting, intergranular, exfoliation corrosion, and stress-corrosion cracking. The article discusses geometric parameters such as pit dimensions, surface roughness, loss of metal thickness, and volume increase due to pillowing to quantitatively characterize the types of corrosion. It also explains the two most common fatigue life assessment methods used in the military aerospace industry: fatigue crack initiation and crack growth analysis.

This article discusses the applications and use of salt spray (fog) testing used to test the resistance of aluminum alloys to exfoliation corrosion. There are two basic types of salt-spray/fog corrosion tests: static condition tests and cyclic condition tests. The article provides a discussion of these tests and indicates the significant differences in each type test used in the combination of weathering and corrosion testing procedures. It also provides information on the test specimen preparation for spray (fog) corrosion tests. Industry specific standards for test specimen procedures often reference the ASTM standards as a basis. The article includes various ASTM standards that describe several cleaning procedures used prior to testing. It describes the major components of a corrosion test chamber.

This article discusses the corrosion resistance of aluminum and aluminum alloys in various environments, such as in natural atmospheres, fresh waters, seawater, and soils, and when exposed to chemicals and their solutions and foods. It describes the forms of corrosion of aluminum and aluminum alloys, including pitting corrosion, intergranular corrosion, exfoliation corrosion, galvanic corrosion, stray-current corrosion, deposition corrosion, crevice corrosion, filiform corrosion, stress-corrosion cracking, corrosion fatigue, and hydrogen embrittlement. The article also presents a short note on aluminum clad products and corrosion at joints.

Most alloys are susceptible to intergranular corrosion, also known as intergranular attack (IGA), when exposed to specific environments. This article reviews the theory and application of acceptance tests for detecting the susceptibility of stainless steels and nickel-base alloys to IGA. It describes the most serious forms of structure-dependent corrosion, such as stress-corrosion cracking and exfoliation, in aluminum alloys including strain-Hardened 5xxx (Al-Mg) alloys and heat treated high-strength alloys. The article concludes with information on the evaluation tests for other alloys such as magnesium alloys and zinc die casting alloys.

Retrogression and reaging (RRA) is an established form of postquench aging heat treatment. RRA treatments can be applied to precipitation-hardened aluminum alloys that are used in aerospace applications. This article provides information on the development background of RRA and the steps involved in the RRA treatments. It discusses the process descriptions, applications, microstructural consequences, and limitations of RRA. In addition, the article describes the influence of RRA on mechanical properties.

This article presents a summary of aluminum temper designations, and applicable aluminum alloys and product forms for temper designations used in the United States (ANSI H35.1), Europe (EN 515), and internationally (ISO 2107).

This article describes the influences of the operational environments of U.S. Navy aircraft during corrosion-control process. The most widely used materials in airframe structures and components, such as aluminum, steel, titanium, and magnesium alloy systems, are reviewed. The article provides information on the inspections steps, corrosion-control issues, and corrosion-prevention strategies for naval aircraft. It contains a table that lists typical locations of corrosion on the aircraft. The article also provides examples of aircraft corrosion damage.

Alloy 2055 is an Al-Cu-Li alloy developed as a replacement for high-strength 7xxx and 2xxx alloys in applications such as fuselage stringers and floor beams. This datasheet provides information on its key alloy metallurgy and illustrates the damage tolerance of 2055-T84 extrusions and 7xxx extrusions.

This article provides a discussion on the design, in-process, storage, and in-field problems and their considerations associated with armament corrosion with examples. Design considerations include geometry, material selection, assembly, pretreatment, coatings, and working and storage environments. In-process corrosion concerns include processing locations, in-process storage of parts, time between processing steps, and quality control of each processing step. The article also discusses the analysis of the in-field corrosion of the finished product, including physical environments, repair of corrosion-protective coatings, general corrosion-protection maintenance, and appropriate fixes and procedures that can be implemented by soldiers in-field to stop continued corrosion of armament equipment.

This datasheet provides information on key alloy metallurgy, processing effects on physical and mechanical properties, and fabrication characteristics of the 2026 alloy.

Aluminum and its alloys are highly corrosion resistant, protected by a self-healing oxide film that effectively passivates the underlying surface. This article examines the various processes by which the protective layer can be breached and the types of corrosion that can occur. It describes pitting, galvanic, and atmospheric corrosion as well as stress-corrosion cracking, corrosion fatigue, and erosion corrosion. It also covers intergranular, exfoliation, filiform, deposition, and crevice corrosion and special cases of corrosion in soils, seawater, and automotive coolant systems. The article provides an extensive amount of data as well as information on coatings, claddings, and cathodic protection methods; the effects of composition, microstructure, and surface treatments; and the compatibility of aluminum with food and various household and industrial chemicals.

This article summarizes the characteristics, material properties, and typical applications of aluminum alloy wrought products. It describes the most widely used worldwide alloy designation system and discusses five major categories, namely flat-rolled products; rod, bar, and wire; tubular products; shapes; and forgings. The article also discusses three widely used indexes to define the fracture resistance of aluminum alloys: notch toughness, tear resistance, and plane-strain fracture toughness. It also describes three types of corrosion attack of these alloys: general or atmospheric surface corrosion, stress-corrosion cracking, and exfoliation attack.

Annealing is an essential treatment in the fabrication of metal parts and semiproducts. This article discusses the processes involved in annealing, namely, recovery, recrystallization, and grain coarsening. It lists the heat treatment conditions of processed aluminum alloys. It provides information on the types of heat treatment, which include preheating, full anneal, stabilization, and stoving. The article describes the steps involved for achieving the age-hardening effect and the strongest hardening effect in aluminum. The steps to increase the strength of aluminum alloys by extremely fine, dispersed second-phase particles are: solution heat treatment, quenching, and age hardening. Finally, the article also discusses the process parameters of annealing, including the effect of strain, effect of temperature, effect of heating rate, and the effect of alloy elements, and the effect of annealing on anisotropy.

This article discusses corrosion fatigue, its effects on the damage tolerance of aircraft, and its predictive modeling. A conceptual framework is presented that incorporates two distinctive cyclic-based life-prediction philosophies and expands them both to include the time domain in order to consider the effects of corrosion. These philosophies include crack initiation used for safe-life design and crack growth used for damage tolerance. The article presents the methodology for computing the effects of real-time age degradation on an aircraft structure for two different corrosion types: crevice and pitting corrosion. It describes the rationale and techniques needed to apply the age-based structural integrity processes to in-service structures in order to realize the benefits throughout the full structural life cycle.

This article includes a collection of color images that aid in the identification and classification of forms of corrosion in industries and environments. It emphasizes the negative aspects of corrosion and examines the cost and the effort to test, evaluate, simulate, and prevent corrosion. The ability of corrosion to undo the best complex engineered systems has been documented.

In high-strength aluminum alloys, stress-corrosion cracking (SCC) is known to occur in ordinary atmospheres and aqueous environments. This article discusses the mechanisms of SCC in aluminum alloys, providing information on two main types of SCC models: those of anodic dissolution based on electrochemical theory and those that involve the stress-sorption theory of mechanical fracture. It reviews three different categories of experiments used to compare SCC performance of candidate materials for service. The categories are tests on statically loaded smooth samples, tests on statically loaded precracked samples, and tests using slowly straining samples. The article describes SCC susceptibility and ratings of SCC resistance for high-strength wrought aluminum products, such as 2xxx, 5xxx, and 7xxx series alloys, aluminum-lithium alloys, and 7xxx alloys containing copper.

This article outlines the processes by which materials are selected to prevent or control localized corrosion, galvanic corrosion, and intergranular corrosion. It reviews the operating conditions and the design of candidate materials for material selection. The article discusses various corrosion-resistant materials, including ferrous and nonferrous metals and alloys, thermoplastics, reinforced thermosetting plastics, nonmetallic linings, glass, carbon and graphite, and catalyzed resin coatings. It examines an unusual form of intergranular corrosion known as exfoliation, which occurs in aluminum-copper alloys. The article also describes three types of erosion-corrosion: liquid erosion-corrosion, cavitation, and fretting. It concludes with information on the various factors to be considered for material selection, including minimum cost or economic design, minimum corrosion, minimum investment, and minimum maintenance.