‘True’ Hard Anodising: What is it and why does it matter?
DECO Australia
Australian-made architectural building products, finishes and protective coatings.
Hard anodising, or hard coat anodising is a valuable metal finishing technique used across a variety of industries, including defence, aerospace, food processing, manufacturing and engineering.
Anodising is a finish for aluminium produced by immersing a metal component into an acid solution. An electrical charge triggers an aluminium oxide layer to form on the surface of the part. This porous skin is then sealed using hydration/water seals, nickel-based seals or organic salts for additional protection. Providing durability, corrosion and wear resistance, anodising is an effective finish for increasing the lifespan of machined components – and its tougher cousin, hard anodising, adds an enhanced level of protection due to a thicker oxidised layer with a denser molecule matrix, suitable for extremely hardwearing applications.
When looking for a hard anodiser, it is important to consider the methods used to achieve this finish. ?Zero-degree hard anodising is an effective process carried out at or below zero degrees Celsius to create a tougher coating. While chemical variations of hard anodising exist, their effectiveness is limited compared to ‘true’ zero-degree hard anodising – highlighting the importance of choosing a true hard anodising process to achieve optimal protection for your components.
Chemical-Based Hard Anodising
A common ‘hard anodising’ method involves adding extra chemicals to the acid baths during the anodising process. A quick and seemingly efficient way to achieve extra hardness using existing anodising tank structures and resources, this form of hard anodising is a substitute process which eliminates the need to adjust the voltage and temperatures of the acid baths. Indisputably easier to achieve, it is typically not as effective, hardwearing or long-lasting as ‘true’ hard anodising.
Zero Degree Hard Anodising: The ‘True’ Finish
To properly achieve the desired hard anodised finish, a zero-degree process must be undertaken. This ‘true’ form of hard anodising involves lowering the temperature of the acid baths to around 0 degrees Celsius. In addition to this, the voltage, and thereby the amperage, running through the baths is increased, and this powerful current and low temperature stimulates the growth of athick, hard and dense aluminium oxide layer. The resulting layer features a dense matrix of pores on the surface, and can be left unsealed for an exceptionally hard, abrasion-resistant coating or sealed for added corrosion resistance.
Why is ‘true’ hard anodising important?
Hard anodising is typically specified for hardwearing applications, such as land vehicles traversing rough terrain, fast-moving machinery parts and components for marine devices exposed to extreme levels of moisture and salt spray. Ensuring your hard anodised finish is properly equipped to withstand demanding applications is essential. While chemical-based hard anodising may wear away and deteriorate faster, true zero-degree hard anodising offers reliable protection that can withstand a wide range of severe conditions, making it the ideal finish for all tough projects.
For more information on anodising and hard anodising, click to download DECO’s new white paper: Finish of The Future: A Comprehensive Guide to Anodising and its Benefits, or contact DECO for more information on DecoUltra? ZD, their trademark Zero Degree hard anodised finish for all essential projects.