<p>To prolonging the service life of the 904L mixing paddle during the phosphoric acid mixing procedure, a series of [Cr-(FeCoNi)₄]Cr_{2.6−<i>x</i>}Al_<i>x</i>Mo_0.4 (<i>x</i> = 1, 1.25, 1.5, 1.75, 2&#xa0;at.%) high entropy alloys (HEAs) were successfully synthesized on the surface of 904L-stainless steel via laser cladding using the cluster–plus–glue–atom framework. The obtained HEA coatings exhibited a single face-centered cubic (FCC) structure, and its microstructure is a typical dendritic structure. With increasing Al content, the microhardness, as well as corrosion, wear and strong acid erosion resistances of the developed coatings, initially increased and then followed a decreasing trend. When <i>x</i> = 1.5, the peak value of microhardness is obtained as 257.2&#xa0;HV_0.2. The wear rate was found to be the lowest, with a value of about 0.93&#xa0;mm³ N⁻¹&#xa0;m⁻¹, nearly one-ninth in comparison to that of the substrate material. The self-corrosion current density was approximately two-thirds compared to that of the substrate. The erosion rate is also the lowest, reaching 0.05&#xa0;mm³&#xa0;h⁻¹, which was lower in comparison to that found for the substrate (0.06&#xa0;mm³&#xa0;h⁻¹), and shows excellent strong acid erosion resistance.</p> Graphical Abstract <p></p>