Abstract: Composite coatings having improved abrasion and dent resistance are described. According to some embodiments, the composite coatings include an outer hard layer and an intermediate layer between the outer hard layer and a metal substrate. The intermediate layer can have a hardness that is less than the hard outer layer but greater than the metal substrate. In this arrangement, the intermediate layer can act as a structural support that resists plastic deformation when an impact force is applied to the coating. In some embodiments, the intermediate layer is composed of a porous anodic oxide material. In some embodiments, the outer hard layer is composed of a ceramic material or a hard carbon-based material, such as diamond-like carbon.

Abstract: Anodic oxide coatings that provide corrosion resistance to parts having protruding features, such as edges, corners and convex-shaped features, are described. According to some embodiments, the anodic oxide coatings include an inner porous layer and an outer porous layer. The inner layer is adjacent to an underlying metal substrate and is formed under compressive stress anodizing conditions that allow the inner porous layer to be formed generally crack-free. In this way, the inner porous layer acts as a barrier that prevents water or other corrosion-inducing agents from reaching the underlying metal substrate. The outer porous layer can be thicker and harder than the inner porous layer, thereby increasing the overall hardness of the anodic oxide coating.

Abstract: Micro additions of certain elements such as zirconium or titanium are added to high strength aluminum alloys to counter discoloring effects of other micro-alloying elements when the high strength alloys are anodized. The other micro-alloying elements are added to increase the adhesion of an anodic film to the aluminum alloy substrate. However, these micro-alloying elements can also cause slight discoloration, such as a yellowing, of the anodic film. Such micro-alloying elements that can cause discoloration can include copper, manganese, iron and silver. The micro additions of additional elements, such as one or more of zirconium, tantalum, molybdenum, hafnium, tungsten, vanadium, niobium and tantalum, can dilute the discoloration of the micro-alloying elements. The resulting anodic films are substantially colorless.

Abstract: Techniques for forming an enclosure comprised of an aluminum alloy are disclosed. In some embodiments, aluminum ions and metal element ions can be dissolved in a non-aqueous ionic liquid in an electrolytic plating bath. A reverse pulsed electric current can facilitate in co-depositing the aluminum ions and the metal element ions onto a metal substrate. The resulting aluminum alloy layer can include nanocrystalline structures, which can impart the alloy layer with increased hardness and increased resistance to scratching, corrosion, and abrasion. In some embodiments, the metal element ion is chromium and the aluminum alloy layer includes a chromium oxide passivation layer formed via a passivation process. Subsequent to the passivation process, the formation of the chromium oxide layer does not impart a change in color to the aluminum alloy layer. In some embodiments, hafnium ions are co-deposited with aluminum ions to form an aluminum hafnium alloy.

Abstract: Dyed anodic oxides having modified dye concentration profiles, and processes for forming the same, are described. The modified dye concentration profiles can be characterized as having a peak of dye concentration beyond at least a specified distance from an outer surface of an anodic oxide. The modified dyed anodic oxides less prone to discoloration, color fading and other cosmetic defects compared to conventionally dyed anodic oxides. The dyed anodic oxides are well suited for implementation on metal surfaces of consumer products, such as consumer electronic products.

Abstract: Oxide coatings that reduce or eliminate the appearance of thin film interference coloring are described. In some embodiments, the oxide coatings are configured to reduce the appearance of fingerprints. In some cases, the oxide coatings are sufficiently thick to increase the optical path difference of incident light, thereby reducing any inference coloring by the fingerprint to a non-visible level. In some embodiments, the oxide coatings have a non-uniform thickness that changes the way light reflects off of interfaces of the oxide coating, thereby reducing or eliminating any thin film interference coloring caused by the oxide coatings themselves or by a fingerprint.

Abstract: Coatings for titanium and titanium alloy substrates are described. The coatings can include an aluminum oxide layer and, in some cases, a thin titanium oxide layer. If the coating includes a titanium oxide layer, the aluminum oxide layer can cover and protect the titanium oxide layer from abrasion and scratching. In some examples, the titanium oxide layer has a thickness sufficient to provide a color by thin-film interference, which can be visible through the overlying aluminum oxide layer. In some embodiments, the aluminum oxide layer is colorized using an anodic dye, pigment or metal colorant, which can combine with interference colors of the titanium oxide layer.

Abstract: Techniques for forming a metal oxide from a metal substrate are disclosed. In some embodiments, the metal oxide can have an optical path difference between about 300 nm to about 1000 nm. The variations in optical path difference can impart the metal oxide to correspond to a range of pre-defined colors. In some embodiments, the optical path difference can impart the metal oxide to have an oxide color that is substantially similar to a color of a housing of a portable electronic device. In some embodiments, the metal oxide can be electrically conductive and the metal oxide can be utilized as an electrical contact of an electronic device to transmit and receive power and data from another electronic device.

Abstract: Colored oxide coatings having multiple oxide layers are described. Processes for forming the multilayer oxide coating can include converting a portion of a metal substrate to a primary oxide layer, coloring the primary oxide layer, and depositing a secondary oxide layer on the primary oxide layer. The primary oxide layer and the secondary oxide layer can be at least partially transparent such that a texture of an underlying metal substrate surface is visible through the multilayer oxide coating. A top surface of the secondary oxide layer can be polished to a high gloss to give the multilayer oxide coating an appearance of depth.

Abstract: Anodic oxide coatings and methods for forming anodic oxide coatings are disclosed. In some embodiments, the anodic oxide coatings are multilayered coatings that include at least two anodic oxide layers formed using two separate anodizing processes. The anodic oxide coating includes at least an adhesion-promoting or color-controlling anodic oxide layer adjacent the substrate. The adhesion-promoting anodic oxide layer is formed using an anodizing process that involves using an electrolyte that prevents formation of delaminating compounds at an interface between the adhesion-promoting anodic oxide layer and the substrate, thereby securing the anodic oxide coating to the substrate. In some cases, the electrolyte includes an organic acid, such as oxalic acid. The anodic oxide coating can also include a cosmetic anodic oxide layer having an exposed surface corresponding to an external surface of the anodic oxide coating. Cosmetic anodic oxide layers can be designed to have a desired appearance or tactile quality.

Abstract: This disclosure relates to rapid and repeatable tests that can be used to evaluate the interfacial adhesion of coatings to substrates. In particular embodiments, tests are used to assess the resistance of anodic oxides to delamination from aluminum substrates. The tests can be conducted using standard hardness test equipment such as a Vickers indenter, and yield more controlled, repeatable results than a large sample of life-cycle tests such as rock tumble tests. In particular embodiments, the tests involve forming an array of multiple indentations within the substrate such that stressed regions where the coating will likely delaminate are formed and evaluated.

Abstract: Techniques for forming an enclosure comprised of aluminum zirconium alloy layer are disclosed. In some embodiments, aluminum ions and zirconium ions can be dissolved in a non-aqueous ionic liquid in an electrolytic plating bath. A reverse pulsed electric current can facilitate in co-depositing the aluminum ions and the zirconium ions onto a metal substrate. The resulting aluminum zirconium alloy layer can include nanocrystalline grain structures, which can impart the alloy layer with increased hardness and increased resistance to scratching, denting, and abrasion. In some embodiments, the aluminum zirconium alloy layer can be anodized to form an aluminum oxide layer. Subsequent to the anodization operation, the oxidized layer is able to retain its substantially neutral color.

Abstract: A process for the corrosion protection of metals such as magnesium, aluminium or titanium, where at least two steps are used, including both plasma electrolytic oxidation and chemical passivation. The combination of these two processing steps enhances the corrosion resistance performance of the surface beyond the capability of either of the steps in isolation, providing a more robust protection system. This process may be used as a corrosion protective coating in its own right, or as a protection-enhancing pre-treatment for top-coats such as powder coat or e-coat. When used without an additional top-coat, the treated parts can still retain electrical continuity with and adjoining metal parts. Advantages include reduced cost and higher productivity than traditional plasma-electrolytic oxidation systems, improved corrosion protection, greater coating robustness and electrical continuity.

Abstract: Processes for enhancing the corrosion resistance of anodized substrates are disclosed. In some embodiments, the process involves a second anodizing operation that targets an area of the substrate that is left inadequately protected by a first anodizing operation, and also targets defects that may have been arisen from intermediate processing operations such as laser-marking operations. The second anodizing operation can be conducted in a non-pore-forming electrolyte, and grows a thick protective barrier film over inadequately protected areas of the substrate, such as laser-marking treated areas.

Abstract: There is disclosed a method for producing corrosion and erosion-resistant mixed oxide coatings on a metal substrate, as well as a mixed oxide coating itself. A surface of the substrate metal is oxidized and converted into a first coating compound comprising a primary oxide of that metal by a plasma electrolytic oxidation (PEO) process. One or more secondary oxide compounds comprising oxides of secondary elements not present in conventional alloys of the substrate metals at significant (>2 wt %) levels are added to the first oxide coating. The source of the secondary element(s) is at least one of: i) a soluble salt of the secondary element(s) in the electrolyte; ii) an enrichment of the surface of the substrate metal with secondary element(s) prior to PEO processing; and iii) a suspension of the secondary element(s) or oxide(s) of the secondary element(s) applied to the oxide of the metal after this has been formed by the PEO process.

Abstract: The embodiments described herein relate to treatments for anodic layers. The methods described can be used to impart a white appearance for an anodized substrate. The anodized substrate can include a metal substrate and a porous anodic layer derived from the metal substrate. The porous anodic layer can include pores defined by pore walls and fissures formed within the pore walls. The fissures can act as a light scattering medium to diffusely reflect visible light. In some embodiments, the method can include forming fissures within the pore walls of the porous anodic layer. In some embodiments, exposing the porous anodic layer to an etching solution can form fissures. The method further includes removing a top portion of the porous anodic layer while retaining a portion of the porous anodic layer.

Abstract: Anodizing techniques for providing highly opaque colorized anodic films are described. According to some embodiments, the methods involve depositing a pigment having a particle diameter of about 20 nanometers or greater into an anodic film. Additionally or alternatively, a barrier layer smoothing operation is used to flatten an interface between the anodic film and underlying metal substrate so as to maximize light reflection off the interface, thereby maximizing light reflected off the pigment that is deposited within pores of the anodic film. The resulting anodic films have an opaque or saturated colored appearance. In some embodiments, the methods involve increasing a thickness of a non-porous barrier layer of the anodic film so as to create thin film interference effects that can add a particular hue to the anodic film. The methods can be used form cosmetically appealing coatings for consumer products, such as housings for electronic products.

Abstract: Processes for cleaning anodic film pore structures are described. The processes employ methods for gas generation within the pores to flush out contamination within the anodic film. The pore cleaning processes can eliminate cosmetic defects related to anodic pore contamination during the manufacturing process. For example, an anodic film that is adjacent to a polymer piece can experience contamination originating from a gap between the anodic film and polymer piece, which can inhibit colorant uptake of the anodic film in areas proximate the polymer piece. In some cases, an alternating current anodizing process or a separate operation of cathodic polarization is implemented to generate hydrogen gas that bubbles out of the pores, forcing the contaminates out of the anodic film.

Abstract: A method for providing a surface finish to a metal part includes both diffusion hardening a metal surface to form a diffusion-hardened layer, and oxidizing the diffusion-hardened layer to create an oxide coating thereon. The diffusion-hardened layer can be harder than an internal region of the metal part and might be ceramic, and the oxide coating can have a color that is different from the metal or ceramic, the color being unachievable only by diffusion hardening or only by oxidizing. The metal can be titanium or titanium alloy, the diffusion hardening can include carburizing or nitriding, and the oxidizing can include electrochemical oxidization. The oxide layer thickness can be controlled via the amount of voltage applied during oxidation, with the oxide coating color being a function of thickness. An enhanced hardness profile can extend to a depth of at least 20 microns below the top of the oxide coating.

Abstract: A process is disclosed for minimizing the difference in thermal expansivity between a porous anodic oxide coating and its corresponding substrate metal, so as to allow heat treatments or high temperature exposure of the anodic oxide without thermally induced crazing. A second phase of higher thermal expansivity than that of the oxide material is incorporated into the pores of the oxide in sufficient quantity to raise the coating's thermal expansion coefficient. The difference in thermal expansion between the anodic oxide coating and underlying metal substrate is reduced to a level such that thermal exposure is insufficient for any cracking to result. The second phase may be an electrodeposited metal, or an electrophoretically deposited polymer. The second phase may be uniformly deposited to a certain depth, or may be deposited at varying amounts among the pores.