hcl consideration of selective precipitation of res through addition of a second acid as precipitation reagent was explored this approach was considered desirable since it reforms in situ the acid hcl used for leaching thus this approach enables acid recovery from the process two reagents that may precipitate mixed re salts are sulfuric acid to form re sulfates of the general formula re 2 so4 3 re nd dy pr and oxalic acid to synthesize re oxalates re 2 c2o4 3 an oxalate precipitate was obtained from the leaching solution by simple addition of oxalic acid resulting in gt 99 yield of re 2 c 2 o 4 3 after optimization with a purity gt 99 an additional benefit of this process is that oxalic acid can be used as a solid reagent thus enhancing the safety of the process furthermore no heat generation was observed with this approach suggesting that this precipitation process is inherently safer and more efficient than the alternative sulfate route which generated substantial heat ndfeb magnets are brittle and can easily be attacked by chemicals magnet manufacturers have found several ways to improve their stability one of the common strategies is to mix the ndfeb materials with a resin to produce so called bonded magnets presence of the resin indeed causes a delay in leaching compared to non bonded magnets however all magnetic material was consumed after stirring in 4 m hcl for 24 h thus suggesting that a longer leaching time would enable complete recovery of res even from these less corrosion resistant materials under selective leaching conditions another common strategy to improve the chemical resistance of ndfeb magnets relies on coating the surface of the magnet with ni since ni has a much higher reduction potential e u00b0 u2212 0.