K. Zakowski

Potential changes in an electric field and electrolytic corrosion

Sources have been described of corrosively hazardous electric fields and methods of determination of the corrosion hazard to metal structures caused by electrolytic corrosion. Results of potential and impedance investigations in the field of stray currents flowing out of a tram traction and in the presence of a defined electric field of low frequency have been presented. Uncertainties have been indicated relating to the generally accepted interpretation principles of measurement results in the presence of electric fields. The possibility has been indicated of incorporating the impedance spectroscopy technique to potential‐voltage investigations, allowing estimation of the real corrosion interaction of stray currents on underground structures.

Studying the effectiveness of a modernized cathodic protection system for an offshore platform

Purpose – The aim of this paper is to present the modernization of an old cathodic protection system installed on the legs of an offshore platform and to discuss the results of the research performed in order to investigate the anticorrosive effectiveness of this solution.Design/methodology/approach – The modernization of the cathodic protection system consisted of connecting to the platform legs a sacrificial anode system placed at the sea bottom. The effectiveness of the modernized system was assessed on the basis of the measurements of the potential profiles of the platform legs, i.e. the distribution of their potential over the entire length.Findings – After connecting sacrificial anode systems, the potential of the legs kept changing towards more negative values. The extent of cathodic polarization increased, and already after a week the potential of the legs fell within the range of full cathodic protection almost along their entire length. The polarization was higher at the lower parts and decrease...

The determination and identification of stray current source influences on buried pipelines using time/frequency analysis

Purpose – The purpose of this paper is to detect the source of stray current interference on underground pipelines in urban areas using a joint time/frequency method of signal analysis.Design/methodology/approach – Investigations are performed on an underground pipeline located in the vicinity of the two direct current tractions: a tramway line and a train line. The results of the analysis are presented in the form of spectrograms, which illustrate changes in the spectral power density of the potential of the rails and of the potential of the pipe in the joint domain time‐frequency.Findings – The comparison of the spectrograms can be used to evaluate if and which stray current source has influence on the investigated metal construction.Originality/value – The combined analysis in the domain of time and frequency can be used as a supplementary one providing new information useful in the evaluation of stray current corrosion hazard. In the presence of several electric field sources in urban areas, this meth...

Study of the formation of calcareous deposits on cathodically protected steel in Baltic sea water

Purpose – The purpose of this paper is to investigate whether the sedimentation of calcareous deposits occurs on cathodically protected steel in Baltic sea water.Design/methodology/approach – Steel electrodes were cathodically polarized in natural Baltic sea water at potential +0.150 V vs Zn electrode in potentiostatic mode. During exposure chronoamperometric measurements were carried out. After the exposure, the electrodes surface was examined by scanning atomic force microscope (AFM) and by scanning electron microscope (SEM). Deposit composition was examined by energy‐dispersive X‐ray spectroscopy (EDX). Comparative investigation was carried out in 1 percent NaCl solution (comparable to the salinity of Baltic sea water).Findings – During cathodic polarization in Baltic sea water, non‐conducting calcareous deposits developed on steel surface. These deposits significantly lowered the cathodic current demand. Morphology and EDX spectroscopy of the deposit indicated that it was built mainly of aragonite (p...

Evaluation and characterisation of the condition of individual components of cathodic protection systems

Results of investigations on a working cathodic protection installation of two underground LPG tanks are presented. The efficiency of anodes and buried reference electrodes were evaluated using electrochemical impedance measurements. On the basis of the impedance spectra obtained it can be shown how one of the anodes attached to the long anode line works inefficiently. In addition, the potential distribution map for the protected tanks is presented. On the basis of this information, an electric connection was revealed from the tanks to the neighbouring reinforced concrete structures, this being inconsistent with the technical guidelines for the cathodic protection installation. The inspection performed on the installation yielded some recommendations concerning the operational parameters and the identification and replacement of defective components.

Detection and time/frequency analysis of electric fields in the ground

Purpose – This paper sets out to detect and characterize electric fields in the ground (such as stray current fields) using a tandem time/frequency method of signal analysis.Design/methodology/approach – Results were obtained from investigations performed in the presence of a generated electric field with controlled variable characteristics, and in the presence of an electric field generated by a tramline. The analysis of measurement registers was performed using Short‐Time Fourier Transformation. The results were presented in the form of spectrograms, which illustrate changes in the spectral power density of the measured signal versus time.Findings – Tandem time/frequency analysis reveals the random or deterministic character of the electric field, enabling its complete time/frequency characteristics to be obtained. Such information is inaccessible using exclusively the frequency analysis methods that utilize classical Fourier transformations. Moreover, an analysis of the spectral power density distribut...