Chromic Acid Anodizing Research Articles

Oxide treatments of Al 1100 for adhesive bonding-surface characterization

A study was made to characterize by spectroscopic methods the surface of oxides formed on Al 1100 by chromate conversion coating, chromic acid anodizing and sulfuric acid anodizing. Adhesive bond strength to silicone rubber was determined using single lap joint specimens, and correlation between the microscopic structure and macroscopic values was found. It was observed that the layer formed in chromate conversion coating was essentially hydrated chromia, and it yielded the lowest bond strength. Sulfuric acid anodizing produced hydrated alumina, incorporating sulfate ions in its matrix; an intermediate bond strength was found with this pretreatment. Chromic acid anodizing gave rise to a compact, almost anhydrous alumina film, and the highest bond strength was attained.

Effect of alloy composition and surface pretreatment on the durability of adhesive-bonded aluminium alloy joints

Boeing wedge test data which indicate the influences of six surface pretreatments and four alloy compositions on the durability of adhesively bonded joints are reported. X-ray photoelectron spectroscopy data which indicate the effects of the same surface pretreatments and alloy compositions on the chemical compositions of the adherend surfaces are summarized. Possible correlations between the durability and X PS data are discussed. Three different methods of modifying the chromic acid anodize (Def 151) treatment of clad alloy adherends, in order to improve durability, are described and discussed.

Oxide morphology and adhesive bonding on titanium surfaces

Titanium metal was subjected to two surface treatments (alkaline peroxide etch and chromic acid anodization) and resulting oxide morphology examined by high-resolution scanning electron microscopy in a Jeol 100-CX STEM. The effects of treatment time in alkaline peroxide upon oxide morphology were followed and parallel mechanical measurements made on the strengths of adhesive bonds between the metal and an epoxy resin. These strengths were measured after a standard environmental exposure, namely 120 h in water at 80° C. As time-of-treatment increases, a micro-porous oxide layer is developed and adhesive strength rises to a maximum. Prolonged treatment with alkaline peroxide produces a drastic fall in adhesive strength accompanied by gross etching of the metal surface without changes in the oxide morphology. The loss of adhesive durability in this case is therefore attributable to surface chemistry effects rather than morphological changes.

Cold-setting adhesives for repair purposes using various surface preparation methods

Abstract The effect of six surface preparation methods on the performance of five adhesives was studied. Comparisons were made using the lap shear test and the Boeing wedge test. It was concluded that only chromic acid etching and anodizing and phosphoric acid anodizing are suitable for permanent primary structure repairs. However, grit blasting and some paste etches may be acceptable for temporary primary structure repairs and for routine secondary structure repairs. Some case histories of actual repairs are included.

The durability of some epoxide adhesive-bonded joints on exposure to moist warm air

Single lap joints bonded with an epoxide adhesive have been exposed to warm moist air for periods up to one year, and then subjected to strength measurement. Surface treatment of the aluminum alloy adherends had an effect upon the ability of joints to resist exposure, the order of surface treatment efficiency in this respect being chromic acid anodize > chromic acid etch > sandblast > degrease. A linear relationship has been observed between joint strength and the water content of joints, leading to the conclusion that water enters a joint by diffusion through the adhesive, rather than by passage along the interface.

Primary Adhesively Bonded Structure Technology (PABST)

The objective of the U.S. Air Force Flight Development Laboratory's Primary Adhesively Bonded Structure Technology (PABST) program awarded to the Douglas Aircraft Company in February 1975, is to improve the structural integrity and durability of future Air Force aircraft while providing significant cost-of-ownership savings (20% goal). Presented is the structural design arrangement selection process which examines static strength, fatigue, and damage tolerance criteria. The surface treatment optimization program, which examines phosphoric acid and chromic acid anodize (using optimized sulf uric-acid/sodium-dichromate [FPL] etch as a standard), is reviewed with current test results. The maximized corrosion resistance afforded by these surface treatments is the key to increased durability. The adhesive selection process is presented with test data. The proposed structural development test plans are discussed. The paper concludes with the projected design, manufacture, and test plans for the full-scale Advanced Development Program (ADP) component. This 52-ft section is the entire cargo compartment of the YC-15 aircraft.

Physical, Chemical, and Crystallographic Characterization of Anodic Coatings on High Strength Aluminum Base Alloys

Durability of adhesive bonded joints in moisture and salt spray environments is essential to USAF aircraft. Structural bonding technology for aerospace applications has depended for many years on the preparation of aluminum surfaces by a sulfuric acid/sodium dichromate (FPL etch) treatment. Recently, specific thin film anodizing techniques, phosphoric acid, and chromic acid anodizing have been developed which not only provide good initial bond strengths but vastly improved environmental durability. These thin anodic films are in contrast to the commonly used thick anodic films such as the sulfuric acid or "hard" sulfuric acid anodic films which are highly corrosion resistant in themselves, but which do not provide good initial bond strengths, particularly in low temperature peel.The objective of this study was to determine the characteristics of anodic films on aluminum alloys that make them corrosion resistant. The chemical composition, physical morphology and structure, and mechanical properties of the thin oxide films were to be defined and correlated with the environmental stability of these surfaces in humidity and salt spray. It is anticipated that anodic film characteristics and corrosion resistance will vary with the anodizing processing conditions.

アルミニウム合金の陽極処理および化学処理皮膜の熱による劣化について

Deterioration of anodic films and chemical films for aluminum alloy by heating was investigated. Material kinds of specimens were 2S and 24S-T4, and surface treatments used were sulfuric acid anodizing, chromic acid anodizing and chemical film treatment.Those finished specimens were heated for 8 hours and 100 hours at 80°C, 120°C, 160°C, and 200°C, respectively.Then, deteriolation of those finishes was examined by salt spray tester, running continuously for 500 hours.Test results are shown in fig. 1 to 6, and summarized as follows:(1) The appearance of specimens, of both anodic coating ane chemical films were some what changed at 80-120°C or higher.(2) After salt spray exposure little or no corrosion attack was found on 2S specimens, but severe one was found on 24S specimens heated to 80°C or higher.(3) Chemical films were more sensitive to heat than anodic coatings.(4) Sulfuric acid anodized 2S specimens were crazed by heating, nevertheless their corrosion resistance were not reduced.

Production and Properties of Opaque Coatings by Chromic Acid Anodising

Production and Properties of Opaque Coatings by Chromic Acid Anodising