Content area
Full Text
ABSTRACT
An enhanced mixed metal oxide (MMO) coating is deposited by arc-plasma spray and chemical processing, the coating consists of Iridium, Tantalum, Titanium and Oxygen resulting in a dense abrasion resistance insert catalytic surface on commercial pure Titanium. The mixed metal oxide is crystalline, electrically conductive coating that activates Titanium and enables it to function as an anode. Such anodes are receiving great attention as an alternative to the conventional anodes in the cathodic protection industry. An experimental investigation was carried out to determine the physical and electrochemical characteristics of a typical MMO anode largely used in deep ground bed installations. The results have shown that such anodes are practically insoluble in acid, have an excellent adhesion to the Titanium tubular substrate, and above all, agreement with reported value of their breakdown potential has been established. The study has also shown that such anodes are not suitable for sulfate-rich environment. The low consumption rate makes these anodes commercially attractive for long term use.
Keywords: MMO anode, Breakdown Potential, Potentiodynamic Polarization, X-Ray, diffraction, and physical and electrochemical characteristics.
INTRODUCTION
It can be appreciated that external corrosion of buried steel structures can be minimized to a tolerable rate using the principles of cathodic protection, whereby an impressed DC current is fed to ancillary anodes from which protective current can travel through the corrosive media, reaching the outside surface of the facilities to be protected [1-4]. Two mostly used methods of CP are the galvanic or sacrificial anode method; and the impressed current cathodic protection. The impressed current cathodic protection is used for larger structures that galvanic anodes could not economically deliver current to provide complete protection. Impressed Current Cathodic Protection (ICCP) systems use anodes connected to a DC power source (a cathodic protection rectifier). Anodes for ICCP systems include silicon, cast iron, graphite, mixed metal oxide, platinum and niobium coated wire [5]. As a consequence, research is focused on finding alternative coatings to protect metal surfaces from corrosion [6]. The latest on the anode technology was the development of non-ferrous anodes, termed as ceramic anodes, where mixed metal oxides are processed to warrant proper electro-chemical behaviour and be cost-effective. One of these developments was the introduction of mixed metal oxides fused on Titanium substrate [7]. The...