to pure magnesium are the magnesium casting alloys with the astm designations as41 am60 az61 az63 az81 az91 az92 hk31 qe22 ze41 zh62 zk51 zk61 ez33 hz32 as well as the wrought alloys az31 az61 az 80 m1 zk60 zk40 moreover pure titanium or also titanium alloys such as tial6v4 tial5fe2 5 etc can be used the chloride free electrolytic bath may contain inorganic anions which are conventional in methods for the plasma chemical anodic oxidation namely phosphate borate silicate aluminate fluoride or anions of organic acids such as citrate oxalate and acetate the electrolytic bath preferably contains phosphate ions borate ions and fluoride ions in combination and in an amount of at least 0 1 mol l of each individual of these anions up to a total of 2 mol l the cations of the electrolytic bath are selected in such a way that they form together with the respective anions salts which are as soluble as possible in order to facilitate high salt concentrations and viscosities this is usually the case in alkali ions ammonium alkaline earth ions and aluminum ions up to 1 mol l in addition the electrolytic bath contains urea hexamethylenediamine hexamethylenetetramine glycol or glycerin in an amount of up to a total of 1 5.