What is hard anodizing?（2）

Type Paint

Hard anodized coatings are commonly used in heavily worn industrial parts, for aggressive or highly corrosive applications. These coatings are usually much thicker and harder than decorative coatings, and usually provide parts with near hard surface or surface hardened steel durability. They can also better penetrate and cover surface defects such as cracks.

Generally, the coating thickness of hard anodized parts exceeds 10 μm (0.01 mm or 0.00004 inch), and the typical coating thickness exceeds 25 μm (0.025 mm or 0.0001 inch). Decorative anodizing usually has a coating of less than 10 μm, and although durable, does not have the same special wear characteristics as anodized hard. Decoration or architectural treatments are usually found on consumer products, such as home cooking utensils, electronic equipment housings and decorations.

Hard-coated articles usually have a dark gray matte surface, although this can vary depending on the composition of the metal and electrolyte solution made. This method can also produce black surfaces and various bronze colors. Decorative anodizing usually produces lighter shadows and can be made matte or shiny. These two types are usually well dyed.

advantage

One of the main reasons for anodizing metals is to make them more resistant to corrosion. The thick outer oxide layer prevents the internal materials from being exposed to moisture, oxygen, and other factors that may cause the metal to decompose. Sealed products are more resistant to corrosion and can usually withstand salt spray for thousands of hours.

The outer coating is also very hard, usually harder than the original metal. In many cases, a thick hard anodized coating may be as hard as tool steel. It is also very wear-resistant, which means it is often used for pistons and other sliding parts that often rub together. Since the oxide layer is part of the metal itself, it will not flake; after anodizing, the metal surface may become rough, but it may need to be worn away to prevent debris from falling off.

Hard anodized metals are usually very insulating, which means they do not conduct heat or electricity well. This is particularly useful for applications that require parts to be used at high temperatures. The coating is also chemically stable and non-toxic.

Extra treatment

Like decorative coatings, hard anodized surfaces can also be dyed, but in most cases, they will remain due to the purely functional nature of most parts. However, they are often impregnated with performance enhancing additives, such as Teflon®, which can improve the self-lubricating properties of the parts. In some cases, they are also sealed in boiling distilled water or dichromate solutions to further improve their corrosion resistance. Disadvantages

The anodized metal has a much lower fatigue strength, which means that it is more likely to break when subjected to pressure, but if the item is sealed, this situation can be improved. Sealing an article will reduce its wear resistance, however, whether a part is sealed usually depends on its end use. Anodizing also cannot protect thin metal objects from damage like dents. The outer coating does make the metal parts thicker, which can become a problem if screw holes or other spaces are drilled in advance.

Materials that can be anodized

Although aluminum is by far the most common hard anodized metal, other materials can benefit from it, including tantalum, magnesium and titanium. In all cases, these treatments can give parts special wear and corrosion resistance, and can be dyed in almost any color. Common uses of hard anodized parts include heavy commercial kitchenware and baking trays, medical prosthetic parts and automotive parts. The military is another big consumer of these products because most hard anodized surfaces meet or exceed strict military specifications.