Can I Weld AL-6XN® to 316L Stainless Steel?

The short answer, is yes! You can weld AL-6XN to 316L.

Theoretically, it is suggested that welding AL-6XN alloy to a 300 series stainless steel is not recommended. However, in reality AL-6XN alloy and 316L stainless steel are welded frequently. This can easily be done using standard welding practices for austenitic stainless steel.

Typically, when welding AL-6XN to 316L tube welds, a consumable weld insert ring is recommended. It will be similar to the process of welding AL-6XN to AL-6XN weld shown in this video.

However, keep in mind that the corrosion resistance can be degraded by making this joint if the conditions are extremely corrosive for the 300 series. Dependent on the severity of the service and if indeed it is a borderline application between AL-6XN and 316L, the mixing of the two metals in the melt most likely would not be attacked.

What is Galvanic Corrosion?

In general, whenever welding two different metals together, it is important to consider the galvanic potential between the two materials.

The higher the potential difference between the two materials, the quicker the failure by consumption of the anode. As the anode is consumed and therefore becomes smaller in comparison to the cathode, the larger the potential difference becomes, further increasing the rate of corrosion.

Can Galvanic Corrosion Occur Between AL-6XN and 316L?

If the intended service is indeed very corrosive, then yes, the heat affected zone just past the weld on the 316L side is more likely to be preferentially attacked. However, the AL-6XN side remains unaffected as long as the application stands good for AL-6XN.

AL-6XN contains higher levels of chromium, nickel, and molybdenum than 316L stainless steel, making it the cathodic material with a higher potential than the anodic 316L. When these two materials are joined together by welding in the presence of an electrolyte (the liquid product), an exchange of current between the anode and cathode is achieved. Chemical segregation of the molybdenum and chromium will occur in the heat-affected zone of the weld area. As the current flows between the two materials, the anodic material (316L) is consumed and becomes less noble and creates the potential for galvanic corrosion.