| 摘要 |
<p>Coatings having high resistance against corrosion esp. by acids at elevated temps. are cathodically formed in a bath contg an alkali molybdate (pref. Na2MoO4) a salt of a transition metal (pref. Ni chloride or sulphate), and an alkali salt of an organic hydroxy acid capable of forming complexes with metallic ions present in the bath (pref. trisodium citrate). The pH is 9-11, pref. 9.5 and the pref. temp. is 20-60 degrees C. The cathodic current density should be above the fissure-formation threshold; it pref. amounts to 6-7 A/dm2. The time of the treatment should be below the 'peeling-off' threshold; pref. 60-90 mins. The coating is subsequently heated at 700-1200 degrees C for 2-24 hrs. in a non-oxidising medium. It can be applied to various steels, Cu, Co, Ti etc. and also to ceramic materials provided with an electroconductive layer.</p> |
