Does IEC60204 allow aluminium conductors?

Yes, IEC60204 allows aluminium conductors. However, copper conductors are preferred, and IEC60204 only allows aluminium conductors with at least 16mm².

While the reason for this is not directly stated in this section of the standard, the reason is not so much that aluminium conductors have a higher resistance per cross-sectional area than copper conductors, but rather that aluminium conductors are more prone to mechanical damage such as breaking, especially when under cyclic mechanical loads.

Source: IEC60204-1:2018+A1:2025, section 12.2