This paper reviews the principles of cathodic corrosion protection and the different ways zinc anodes are applied to reinforced concrete through wire arc spraying. It also explains how the lifetime of zinc coatings can be extended with an organic topcoat and presents related test data. Paper includes a German-language abstract.

Structural damage in concrete structures caused by corrosion is widespread and demand comprehensive repair work. The additional installation of an active corrosion protective systems for structures being located in unfavourable conditions is imperative. Thermally sprayed coatings serving as anode have been adapted from the cathodic protection of steel. These systems have gained attention as they offer advantages in efficiency and lower cost. Thermally sprayed zinc coatings are applied to new steel reinforced concrete structures or those which are subject to re-structuring. In this contribution, the capability of various systems is examined by field tests in a marine structure and in different laboratory tests under natural and under accelerated conditions.

Structural damage caused by corrosion in concrete structures is widespread and requires extensive repair work. The installation of corrosion protection systems for constructions that are under unfavorable conditions is urgently necessary. Thermally sprayed coatings serving as anode have been developed from the cathodic protection of steel. These systems have attracted attention because of their performance and lower cost advantages, and they are about to enter the competitive anode system market. Thermally sprayed zinc coatings are applied to the surfaces of steel-reinforced concrete components that are affected by corrosion. In this article, the ability of the system to deliver a protective current is verified by field tests in a marine structure in the Arabian Gulf that was discussed in 1997. Paper includes a German-language abstract.

Thermal-sprayed titanium coatings were investigated as anodes for impressed current cathodic protection systems for steel reinforced concrete structures. The coatings were applied by twin-wire thermal-spraying using air and nitrogen as atomizing gases. The coatings were non-homogeneous due to oxidation and nitridation of the molten titanium with the atmospheric gases oxygen and nitrogen. The primary coating constituents were α-Ti (containing interstitial nitrogen and oxygen), γ-TiO and TiN. Nitrogen atomization produced coatings with less cracking, more uniform chemistry, and lower resistivity than air atomization.

Steel-reinforced concrete slabs coated with a thermal-sprayed titanium anode were used to simulate impressed current cathodic protection systems. The titanium anodes were activated with a cobalt nitrate catalyst and subjected to accelerated electrochemical aging representing approximately 23 years at 0.00215 A/m 2 (0.2 mA/ft 2 ). During the aging experiment, current was kept constant at 0.0215 A/m 2 (2 mA/ft 2 ), voltages were recorded, and water was applied periodically when voltages exceeded compliance levels. At the end of the experiment, coating resistivity, adhesion strength, and titanium-concrete interfacial chemistry were determined. Results show that the coating resistivity increases and adhesion strength decreases with electrochemical aging. Voltages for the slabs varied with the relative humidity. Electrochemical reactions at the titanium-concrete interface caused deterioration of the cement paste by leaching of calcium compounds. Accelerated aging results are compared to similar ones for an uncatalyzed titanium anode and to results from the Depoe Bay Bridge.

A review of selected national and international thermal spraying guides and specifications for the preservation of steel and reinforced concrete using thermal spray coating of aluminum, zinc and their alloys is presented. The work program and current status of the US national organizations contributing to and developing test methods and process standards are summarized along with those of ISOATC 107/SC 5. The Secretariat of the ISO/TC 107/SC 5, Thermal Spraying was transferred from AFNOR, France, to ANSI, US, in June 1995. ANSI, in turn, designated AWS to be its delegate in thermal spray matters. The work program of the newly formed SSPC/NACE/AWS Tri-Society Committee on thermal spray coatings for the corrosion protection of steel is summarized.

Considering the number of concrete structures such as bridges, overpasses, trestles etc., their maintenance and repair form a significant part of the highway administration budget. Cathodic protection is becoming more popular because it helps reduce maintenance and renovation costs. Arc-sprayed zinc and zinc/aluminum alloy coatings are widely used in cathodic protection systems. The surface preparation of concrete is critical to the quality of coating and hence, the quality of the cathodic protection. Typically, sandblasting with surface brushing is used as preparation. This method has several technical, economic and ecological deficiencies: weather/humidity limitations, difficult removal of organic contaminants from the surface, an irrevocable loss of blasting media, high dust level, etc. An objective of this proceeding is to describe a plasma cleaning process as a successful alternative to sandblasting and to show the possibilities of combined plasma cleaning/coating process for the cathodic protection of reinforced concrete structures. This environmentally friendly process will result in better anodic coatings at lower cost and fewer concrete structure repairs.