Sulphuric hard anodising, also known as Type III anodising, is an electrochemical process that creates a thick and highly durable oxide layer on the surface of metal substrates, typically aluminium and its alloys. Unlike sulphuric soft anodising (Type II), which produces a relatively thin oxide layer, sulphuric hard anodising results in a significantly thicker and harder coating.
During the sulphuric hard anodising process, the metal workpiece is immersed in a sulphuric acid electrolyte solution and subjected to a controlled electrical current. This causes oxidation of the metal surface, forming a dense and abrasion-resistant layer of aluminium oxide. The thickness of the oxide layer produced during hard anodising tend to be around 50 microns, depending on the specific application requirements.
The resulting hard anodised coating provides several key benefits, including exceptional wear resistance, improved corrosion resistance, increased surface hardness, and enhanced thermal and electrical insulation properties. These properties make hard anodising ideal for applications requiring high levels of durability and performance, such as aerospace components, automotive parts, industrial machinery, and electronic devices.
