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Electropolishing is essentially a “reverse plating” technique. By using a combination of chemicals and electrical current, electropolishing carefully removes surface imperfections and contaminants from metal parts (and can be used for removing heat tint and oxide scale). Precise monitoring removes as little as .0001″ up to .0015″ (per surface) to produce the desired result.
This degree of precision and consistency, along with the ability to remove a variety of surface imperfections in one process, is why electropolishing is so often specified for critical parts used in medical implants and surgical instruments, aerospace components and fragile or critical parts used in other industries. Electropolishing is a one-stop process for a micro-smooth, ultraclean, corrosion and pathogen-resistant surface finish – with 30 times more corrosion resistance than passivation.
Electropolishing also eliminates the need for additional metal finishing processes like hand deburring, tumbling, pickling, and cleaning.
The electropolishing process is often used as a more aggressive alternative to passivation (per ASTM B912 and ASTM A967) and does not require a separate treatment for passivation. Since the process removes the outer skin of metal, embedded contaminants which can cause sub-surface corrosion are eliminated. The electropolished part is left in a homogeneous and passive condition which offers superior corrosion resistance to chemical passivation.
Chromate conversion coating is a type of conversion coating used to passivate steel, aluminium, zinc, cadmium, copper, silver, titanium, magnesium, and tin alloys. The coating serves as a corrosion inhibitor, as a primer to improve the adherence of paints and adhesives, as a decorative finish, or to preserve electrical conductivity. It also provides some resistance to abrasion and light chemical attack on soft metals.
Chromate conversion coatings are commonly applied to everyday items such as screws, hardware and tools. They usually impart a distinctively iridescent, greenish-yellow color to otherwise white or gray metals. The coating has a complex composition including chromium salts, and a complex structure.
Chromate conversion coatings are usually applied by immersing the part in a chemical bath until a film of the desired thickness has formed, then removing the part, rinsing it, and letting it dry. The process is usually carried out at room temperature, with a few minutes of immersion. Alternatively, the solution can be sprayed, or the part can be briefly dipped in the bath; in which case the coating reactions take place while the part is still wet.
The coating is soft and gelatinous when first applied, but hardens and becomes hydrophobic as it dries out, typically in 24 hours or less.
MIL-A-8625 Type II / Type 2 Sulfuric Anodizing
Base Materials that MIL-A-8625 Anodize Type II sulfuric anodizing can be applied include 1100, 2000, 3000, 5000, 6000, and 7000 series aluminum alloys
Sulfuric Anodizing is a process that provides a conversion on aluminum which changes the surface of the material to a naturally occurring aluminum oxide. The oxide build up changes the surface of the aluminum which then provides greater abrasion resistance as well as increased corrosion protection (roughly 336 hours per ASTM B117). The finish from sulfuric anodizing will not only build up the aluminum oxide on the surface 0.0002″ – 0.0003″ thick, but will also penetrate into the material the same amount. Other than a clear anodize this coating may also be dyed in various colors. The typical industry colors include black, clear, green, gold, red, and blue. One other interesting property of the aluminum oxide is that it is a great electrical insulator.
MIL-A-8625 Type III / Type 3 Hard Coat Anodizing
Base Materials that MIL-A-8625 Anodize Type III hard coat anodizing can be applied include 1100, 3000, 5000, 6000, and 7000 series aluminum alloys. Please note that we are unable to hard anodize 2000 series aluminum due to the high copper content.
Hard anodizing is a phrase used to describe an anodizing coating where the need for surface hardness and abrasion resistance is the main criteria. The build up for hard coat anodizing is much thicker than your standard anodizing. The typical build up of this coating is 0.001” and also 0.001” penetration into the material. The color of the aluminum oxide build up from hard coat anodizing depends greatly on the alloy of the aluminum material. The color can range from a champagne/gold hue to a dark gray.
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