Aluminum has dramatically impacted the way manufacturers design and build their products since its introduction over a century ago. It’s combination of strength, light weight, versatility and corrosion resistance make it a cost effective choice for any industry. No material is perfect, however, and as resilient as aluminum is, it may be necessary to add special wear resistant coatings to your aluminum products to help extend their service life.
There are many options available for aluminum coatings. It’s helpful to partner with an experienced and knowledgeable material supplier who can answer questions about the advantages and shortcomings regarding each type of coating.
Reasons to add a coating to aluminum
For applications that will undergo a great deal of pressure and stress, aluminum can accept many different types of surface coatings that add to its corrosion resistance, lubricity, wear resistance and durability. Some of these treatments are purely aesthetic, such as paint, powder coating or colored anodizing. Other coatings are necessary to extend the life of the product.
When using aluminum in plastic injection mold applications, it may be necessary to coat the core and cavity surfaces of the mold with a wear resistant coating to protect the material from the abrasive nature of some resins.
Some automation applications, such as the conveyor systems used in distribution facilities, require coatings to protect aluminum components from the constant wear they receive from processing millions of packages and parcels over their service life.
What are the requirements of a wear resistant coating?
When adding a wear resistant coating, certain requirements must be met. First, while many people assume that hardness is one quality that indicates a substance’s ability to withstand wear, it’s more accurate to look at the relationship between the material’s hardness and stiffness. There’s a subtle difference between these two qualities, with the former measuring the metal’s resistance to localized surface deformation, and the latter indicating its ability to resist elastic deformation after a load has been applied.
Second, it’s important for a wear resistant coating to have a low amount of friction between the coating and the wearing counterpart. While this is not technically a matter of how resistant a material is, if the surface coating is less prone to creating friction, it will reduce the amount of energy transfer between two sliding surfaces and therefore suffer less wear and tear.
Third, a protective coating should have some load-bearing capability. This can be achieved with a very thick coating or by strengthening the base metal’s surface via diffusion into the lattice.
The main types of wear resistant coatings
Anodizing is one of the most common surface treatments for aluminum alloys. Hardcoat anodizing is a process that generates an aluminum oxide layer that penetrates the metal’s surface. It uses a suitable electrolyte, usually a sulfuric acid bath, to actuate the process. The longer it spends in the bath, the thicker the coating. A hard anodized coating will feature increased wear resistance and a smoother finish than the standard anodizing process.
Plasma electrolytic oxidation is also an option. This is an electrochemical surface treatment process that will generate a protective oxide coating on aluminum. Like anodizing, the higher potentials and resulting plasma modify the oxide layer’s structure. The finished results lead to greater hardness and increased protection against wear, corrosion, heat and electricity.
Nickel plating is a time-tested method for providing a wear resistant coating to aluminum parts, but one that has fallen out of favor in recent years. It is an electrolytic process involving a solution bath and electrical current to facilitate the plating. The environmental concerns and costly disposal of used nickel plating solution has made this a less attractive option for contemporary manufacturing concerns.
Electroless nickel plating adds a protective layer of nickel without the need for electrolytic processing. The metal is submerged in a chemical solution that contains nickel salt and a phosphorus reducing agent. The process does not require electricity and relies entirely on a chemical reaction. The resulting surface is less porous than other options; it has higher hardness, better wear resistance and more resistant to corrosion.
Your Technical Services Professional
Clinton Aluminum is the Midwest’s leading supplier of aluminum and stainless steel plate products. If there are questions about wear resistant coatings, contact a friendly and knowledgeable customer service representatives today.