Corrosion Resistance of Pipeline Steel with Damaged Enamel Coating and Cathodic Protection

Abstract

This paper presents the first report on the corrosion resistance of pipeline steel with damaged enamel coating and cathodic protection in 3.5 wt % NaCl solution. In particular, dual cells are set up to separate the solution in contact with the damaged and intact enamel coating areas, to produce a local corrosion resistance measurement for the first time. Enamel-coated steel samples, with two levels of cathodic protection, are tested to investigate their impedance by electrochemical impedance spectroscopy (EIS) and their cathodic current demand by a potentiostatic test. Due to its glass transition temperature, the enamel-coated pipeline can be operated on at temperatures up to 400 • C. The electrochemical tests show that cathodic protection (CP) can decelerate the degradation process of intact coating and delay the electrochemical reactions at the enamel-steel interface. However, CP has little effect on the performance of coating once damaged and can prevent the exposed steel from corrosion around the damaged site, as verified by visual inspections. Scanning electron microscopy (SEM) indicated no delamination at the damaged enamel-steel interface due to their chemical bond.

Microwave cladding of Inconel-625 on mild steel substrate for corrosion protection

“…Mild steel is the most commonly used material in engineering applications; but it has very poor corrosion resistance. The surface properties of a ferrous alloy can be modified through various methods, such as heat treatment, PVD, thermal spraying, epoxy coating, enamel coatings, laser cladding, and microwave cladding [2][3][4][5][6]. Thermal spraying is the most commonly used technique due to its ease of operation and ability to deposit a range of materials on a substrate.…”

“…However, the weak mechanical bonding between splats and the significantly higher porosity are the major limitations associated with the thermal spray technique [7][8][9]. Epoxy coatings are widely used in natural gas and crude oil pipelines, but these coatings exhibit weak bonding with their steel substrates and therefore they are subjected to under-film corrosion [6]. Enamel coating has excellent resistance to abrasion and mechanical shocks particularly in extreme wear and erosion applications.…”

Cr3C2-NiCr Coating for the Protection of API Steel Corrosion in Concentrated Sodium Chloride Solution

“…The protection of pipeline steel by the use of inorganic coatings has been reported by many researchers [19][20][21][22]. Fan et al [19,20] investigated the protection of pipeline steels enamel coatings, while Chatha et al [21] studied the effect of the Cr 3 C 2 -NiCr coating layer on the corrosion protection of T91 boiler steel under different types of environments.…”

“…The protection of pipeline steel by the use of inorganic coatings has been reported by many researchers [19][20][21][22]. Fan et al [19,20] investigated the protection of pipeline steels enamel coatings, while Chatha et al [21] studied the effect of the Cr 3 C 2 -NiCr coating layer on the corrosion protection of T91 boiler steel under different types of environments. The authors [21] claimed that this coating offers a high melting point and maintains high hardness, strength and wear resistance up to a maximum operating temperature of 900 • C. Tillmann et al [22] also claimed that the Cr 3 C 2 -NiCr coating features a very low porosity, low oxidization and low carbide decomposition or carbide-matrix dissolution, which leads to increasing hardness and abrasion resistance.…”

Special Issue: “Coatings for Harsh Environments”

“…However, when damaged the efficacy might be compromised. Evaluation of these coatings when damaged offers new insights into the behaviour of these coatings [13].…”