Thermal-sprayed zinc anodes are used in impressed current cathodic protection systems for some of Oregon's coastal reinforced concrete bridges. Electrochemical aging of zinc anodes results in physical and chemical changes at the zinc-concrete interface. Concrete surfaces heated prior to thermal-spraying had initial adhesion strengths 80% higher than unheated surfaces. For electrochemical aging greater than 200 kC/m 2 (5.2 A-h/ft 2 ), there was no difference in adhesion strengths for zinc on preheated and unheated concrete. Adhesion strengths decreased monotonically after about 400 to 600 kC/m 2 (10.4 to 15.6 A-h/ft 2 ) as a result of the reaction zones at the zinc-concrete interface. A zone adjacent to the metallic zinc (and originally part of the zinc coating) was primarily zincite (ZnO), with minor constituents of wulfingite (Zn(OH) 2 ), simonkolleite (Zn 5 (OH) 8 Cl 2 H 2 0), and hydrated zinc hydroxide sulfates (Zn 4 S0 4 (OH) 5 xH 2 0). This zone is the locus for cohesive fracture when the zinc coating separates from the concrete during adhesion tests. Zinc ions substitute for calcium in the cement paste adjacent to the coating as the result of secondary mineralization. The initial estimate of the coating service life based on adhesion strength measurements in accelerated impressed current cathodic protection tests is about 27 years.

Steel reinforcement corrosion is one of the most serious causes of the premature deterioration of North American bridges and parking garages. Carbon steel rebars are very vulnerable to corrosion in salt contaminated concrete from deicing or coastal environment since the chloride ions induce severe corrosion as they reach the reinforcing steel rebars and depassivate the carbon steel. This paper evaluates the potential of using stainless steel coatings as a means to protect steel rebars from corrosion, especially in a salt contaminated concrete environment. The 316 L stainless steel coated coupons and rebars were prepared using Arc-sprayed and HP/HVOF processes. The corrosion performance of coatings were evaluated using linear polarization, a.c. impedance and salt spray techniques. Metallographic examination was also performed to characterize the coating microstructure.

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.

This paper reviews some data regarding the combined effect of erosion and corrosion of thermal spray ceramicmetallic coatings and their potential application in sea water and production systems for the oil industry. The paper also presents recent research results from SINTEF Corrosion and Surface Technology with respect to development of new and better ceramic-metallic coatings from the Norwegian coating industry. It has been shown that taking new high velocity spraying technology into use in combination with recent developed powders, the result is a more corrosion and erosion resistant coating than the traditional and most often specified type Praxair LW45.

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.