Improved Ceramic Anodes for Corrosion Protection.
CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL
Pagination or Media Count:
Ceramic anodes used for cathodic protection are currently made with expensive metals niobium, tantalum as substrates, and these anodes have a limited useful life. This study investigated plasma-sprayed ceramic coatings on aluminum and stainless steel substrates, as well as solid sintered ceramics, as less expensive and longer-lived alternatives. Anodes made of stainless steel substrates with an electroplated coating of a passive metaltantalum followed by a lithium-ferrite plasma-sprayed coating showed excellent promise. However, a triple layer plasma-sprayed coating system consisting of lithium ferrite over niobium over Ni-Cr-Al-Y sealcoat on 316L stainless steel and aluminum alloy substrates proved unacceptable as a possible anode material because of severe cracking and spalling. Solid sinter Mn and Mn-Zn ferrites also showed potential. They were fabricated with careful control of the postsintering cooling rate to yield materials with anodic dissolution rates less than 0.5 grams per amp year gA-yr. This is considerably improved from the 1 to 2 gA-yr previously reported for plasma-sprayed lithium ferrite on a valve metal substrate. Donor doped and reduced solid sintered titanate compounds yielded electrically conductive materials, but they broke down so quickly and severely under anodic polarization testing that they are not suitable for cathodic protection applications. Originator-supplied keywords include Anodic coatings.
- Coatings, Colorants and Finishes