How Can I Plate Anodize Stainless Steel?

Anodization is the process of treating a metal, generally aluminum, in a bath full of electrolytes. When an electric current is passed through the bath, metal oxides accumulate on the metal surface, strengthening it and protecting it against corrosion and abrasion. Generally, anodization is not used for stainless steel because steel oxidizes when anodized, causing flaking and exposing the underlying metal to corrosion. Steel, however, can be plated with aluminum, then anodized using typical aluminum anodization techniques. Anodizing plated steel will strengthen its surface and, should the surface ever be painted, will facilitate its stronger adhesion with paint.

Things You'll Need

  • Chemical-resistant bath, often ceramic
  • 2M sulfuric acid
  • Current source
  • Two-electrode system
  • Magnetic stir bar
  • Stir plate
  • Vacuum environment
  • Aluminum ion source
  • Ion gun
  • Platinum sheets
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Instructions

    • 1

      Use ion vapor deposition (IVD) to deposit aluminum onto the surface of stainless steel. In a vacuum environment, use an ion gun to bombard the stainless steel surface with ions of an inert gas in order to clean the surface. Next, use an ion gun to bombard the stainless steel surface with aluminum ions, until the surface is thoroughly coated with an aluminum film.

    • 2

      Prepare the bath for anodization. Pour 2M sulfuric acid into the bath, and connect it to a voltage charger that will provide between 40 and 100 V.

    • 3

      Set up the two-electrode system. Connect platinum sheets to the cathode, and connect aluminum-coated stainless steel to the anode. Oxide ions will accumulate at the anode when the voltage current is turned on, thus anodizing the plated stainless steel. The cathode will produce hydrogen ions and positive current to cancel out negative current produced at the anode.

    • 4

      Drop a magnetic stirring bar into the bath, and place it on top of a stir plate. Turn on the stir plate. Regular circulation of electrolyte will prevent preferential accumulation of oxides onto a particular area of the object, and will prevent any areas of the bath from overheating.

    • 5

      Turn on the current source, and immerse the two-electrode system in the bath. Keep bath temperature between 5 and 18 degrees Celsius to avoid dissolution of metal oxide layer. Leave the object in the bath for several minutes.

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