Dorsetware Limited

Whilst Steel and Aluminium can create a harsh reaction when met under certain conditions, anodised aluminium and stainless steel can be used together with less worry. This is because they have undergone processes that help to prevent the reaction between the two core materials. 

In this blog, we will explore the reaction between steel and aluminium, how to prevent the reaction and answer other frequently asked questions around anodising, passivation and the benefits of these processes. 

The Reaction Between Aluminium & Steel 

When aluminium and steel, in their unaltered forms, come into contact with one another, there is a potential for a reaction known as galvanic corrosion. 

Galvanic corrosion is an electrochemical process that occurs when two different metals make contact while immersed in an electrolyte solution such as water. This causes the anodic metal to corrode whilst the cathodic metal stays intact. In this case, Aluminium is the anodic metal. 

Severe corrosion is likely to take place in wet or damp environments, such as in the ocean. 

How To Prevent Corrosion 

There are multiple ways that you can prevent or reduce corrosion. One method is to apply a thin layer of corrosion-resistant coating or paint to isolate the materials, creating a protective barrier that prevents direct metal-to-metal contact. Epoxy or anti-corrosion primer is good for this. This can also be done by separating the two metals with a thin layer of insulating material such as rubber or plastic. 

When bringing aluminium and steel into contact, it’s essential to prevent corrosion. Another way this can be achieved is by altering the material’s qualities. Aluminium can be anodised, and steel can be made stainless. 

What is Anodised Aluminium? 

Anodised aluminium is aluminium that has undergone an electrolytic process to create a hard, durable and corrosion-resistant oxide layer on its surface. This layer is an integrated part of the aluminium itself; it is not a coat that can be peeled off or chipped. 

The anodising process involves immersing the aluminium in an electrolyte bath and sending an electric current through it, encouraging the formation of the protective oxide layer. 

To learn more about anodising, read our blog here. 

What is Stainless Steel? 

Stainless steel is an iron-based alloy made by melting iron with a minimum of 10.5% chromium and other alloying elements like nickel, silicon, and molybdenum in an electric arc furnace. The result is a material that has a self-healing chromium oxide layer on its surface, which provides excellent resistance to corrosion and staining.  

Steel Passivation vs Anodising: What is the Difference?  

Steel passivation is a chemical process exclusive to steel that enhances the chromium oxide layer for better corrosion resistance. Anodising, on the other hand, is an electrolytic process for aluminium and other light alloys that builds an oxide layer. The main differences are the materials they treat and the methods that are used, but both are used as a way to make the respective materials more durable and corrosion-resistant. 

If you want to know more about steel passivation, read our blog here. 

Do Anodised Aluminium & Stainless Steel Have a Reaction? 

Anodised aluminium and stainless steel do not have an inherent chemical reaction compared to their raw counterparts. The oxide layer on both materials acts as a barrier that prevents direct electrical contact and slows down the galvanic corrosion process.  

However, in the presence of an electrolyte, such as water or moisture in the air, they form a galvanic couple, which speeds up the corrosion process. Regular maintenance, proper insulation, and the use of steel passivation can effectively address these issues. 

Can you Anodise Stainless Steel? 

Stainless steel cannot be anodised in the traditional sense, as this process is primarily used for metals like aluminium, titanium and magnesium. Stainless steel already has a corrosion-resistant oxide layer, and this layer is not porous and cannot be thickened by the anodising process. 

However, similar protective finishes can be achieved on stainless steel through alternative methods like Physical Vapor Deposition (PVD) coatings or steel passivation. 

In a nutshell… 

Whilst raw aluminium and steel can react and corrode when exposed to certain conditions, processes like anodising aluminium and passivating stainless steel provide effective protection. These treatments strengthen the oxide layers on each metal, reducing the risk of galvanic corrosion and making them safer to use together. By understanding how these processes work, as well as applying additional preventative measures such as coatings or insulation, you can extend the lifespan and durability of both materials in a wide range of environments. 

At Dorsetware, we offer a range of services, including anodising aluminium and steel passivation. If you are interested, get in touch today!  You can reach us using our online contact form, or if you’d prefer to speak to our team directly, call us on 01202 677939. Or explore our site to see our services.