The most popular color Pioneer offers for aluminum parts is the Black version of anodizing. Over the past 74 years we have invested significant efforts into the research and development of the most robust, flexible, and aesthetically appealing version of this process.
We offer both standard Type II black anodize as well as a more specialized Type III Hardcoat black anodize. In addition we offer specialty processes such as Optical Black™, Black Enduraguard™, MediBlack™, and ARP Black as solutions for extreme applications and to also address some fundamental challenges certain aluminum alloys present.
Both the Type II standard black anodize and the Type III Hardcoat black anodize require an immersion in an organic dye bath after the application of the anodize coatings. The standard anodize and the Hardcoat anodize processes result in coatings that contain micro-porosity. The dye is absorbed in these pores causing the coloration. In general a minimum of .0004” thick standard anodize and .001” thick of the Hardcoat anodize is required to get a deep black color.
The Anodize process creates a conversion coating of a hard aluminum oxide that penetrates into the base aluminum while also growing from the base dimension. This results in a coating that if breeched will not be subject to creep corrosion like paints and plating processes. Type II standard anodized coatings are best for aesthetic applications while still producing a corrosion and wear resistant coating that will not chip or scratch like painted or plated finishes. Type III black anodized coatings will provide maximum corrosion resistance lasting up to 2000 hours in salt spray testing. The Type III black anodize is also best for wear resistance with durability equal to hardened 70 HCR steel.
The black dye material used for these processes is critical in producing the final hue of the black color. The makeup of this dye also has a dramatic impact on how fade resistant the finished parts will be when exposed to both sunlight and indoor ultra-violet lighting.
Many black dyes can produce blueish or reddish coloration when compared to neutral black colors. This hue comes out strongly when poorly dyed or sealed black dyed finishes are exposed to strong UV light, such as sunlight or fluorescent lighting in display cases, with the initial black color fading to purple or light brown in very short timeframes. Pioneer has worked to specially formulate a neutral black version of our dye. Our “Pioneer Black” dye exhibits the maximum light fastness qualities available in the marketplace, and compares favorably to electrolytic black in many applications.
After parts have been anodized and dyed black, the pores in the coating are sealed to enhance the durability of the coating for both corrosion resistance and light fastness. The most common sealing options are to utilize either a nickel acetate or nickel fluoride seals. Our research shows that the nickel fluoride seal has a significant impact on providing the maximum light fastness for anodized coatings. In addition we have determined that a heavier coating thickness can also improve the resistance to fading over time. Applications of standard anodize with .0007” minimum of coating would be recommended for outdoor applications.
The appearance of black anodized parts is also impacted by the surface finish of the parts. Components that have a dull finish in the raw will be dull in appearance after anodize. Dull finished parts will have a matte black final appearance. A duller finish can be produced either by mechanical blasting or chemical etching of the parts in their raw state. Conversely raw product will need to be either mechanically or chemically polished to produce a shiny, deep black finish after processing. Pioneer offers blasting and chemical etching processes as well as chemical polishing (bright dip) to provide a custom look.
The black anodize and Hardcoat black finishes are approved for indirect food contact, as accepted for use by the ELV, RoHS, and Weee environmental directives. This allows black anodize finishes to be used in a variety of industrial and aesthetic markets and applications.
Pioneer also offers another version of our black anodize which entails the use of a metallic colorant that is deposited into the pores of the anodized coating. We call this process Optical Black™ anodize. This process is recommended when our customers need their parts to hold up to the rigors of high intensity laser lighting without breakdown of the coloring agent. This process will not produce as deep of a black color and is not suitable for all aluminum alloys such as castings, 2000 series, and 7000 series aluminums. By using this Optical Black™ anodize process our customers can utilize aluminum components with a permanent black color for maximum light absorbance without the risk of the colorant breaking down and clouding sensors and mirrors that are common to this type of equipment.
When our customers need their products to hold up to the aggressive nature of sterilization seen in the medical industry, we recommend our Medi-Black™ anodize process. This process combines the use of the Optical Black™ anodize process with a final dye of the organic Pioneer black dye. This results in a finish that will not fade when exposed to neutral pH sterilization and autoclave cycles.
The nature of Die cast aluminum makes it a poor choice for highly corrosion resistant and aesthetically pleasing black anodize finishes. Pioneer has developed the Black Enduraguard™ process as a solution to this challenge. Enduraguard™ entails applying the .0003-.0004” maximum thickness of standard black anodize that is attainable with this alloy and then it is followed by the application of a specially developed black sealant. The black seal is applied at a thickness of approximately .0003”-.0005”. The natural appearance of standard black anodize on die cast aluminum is a grayish black with an uneven mottled appearance. The final appearance of Black Enduraguard™ is a uniform semi-bright black coating. This coating has the maximum performance for corrosion resistance lasting 5000 hours in salt spray testing with little to no signs of corrosion. This process is also resistant to creep corrosion. In addition this finish is very resistant to low and high pH chemicals that would normally breakdown standard black anodize coatings.
Another option for Die Castings is the ARP Black process, which includes etching the casting in a strong fluoride based chemical bath prior to anodizing and dyeing steps. The black color is not as deep as with wrought alloys, but dramatically improves the appearances of a pressure die cast component compared to a traditionally anodized die casting appearances.
For over 74 years, Pioneer Metal Finishing had developed and produced billions of parts with black finishes, each developed to be best in class. Pioneer has test results we can share and we can also process samples to assist you in engineering the best Black version of an anodized coating to meet your application needs.