The dissolution kinetics of hydrogen-charged carbon steel in mixtures of NS4 solution and borate buffer simulating the electrolyte under a delaminated coating on an underground pipeline. It has been shown that the active dissolution of iron in environments with near-neutral pH is considerably accelerated by hydrogen absorption by the metal. This effect can result in local corrosion, in particular, stress corrosion cracking of steel structures. Currently, the majority of failures that occur on high pressure buried pipelines result from local corrosion, primarily stress corrosion cracking (SCC) of the metal under delaminated insulating coatings [1, 2]. In view of this, systematic studies carried out in many countries all over the world deal with the corrosion behavior of low-alloy and carbon steels in environments simulating the so-called subfilm electrolyte, i.e., solution in the corrugated parts of an underground pipeline coating. To study the SCC of pipe steels, the NS4 solution is often used as the test environment; this solution was formulated on the basis of analyses of liquids found under delaminated underground pipeline coatings [3]. It has been shown that the corrosion potential of low-alloy and carbon steels in this environment corresponds to the active dissolution region of such steels [3 - 5] and hence the metal should corrode rather uniformly.1. However, it has been noted that a local corrosion site (pit or crevice) is formed on the steel surface upon a small cathodic shift of potential from the corrosion potential; this effect is believed to result from hydrogen absorption by the metal [3 - 9]. In fact, hydrogen absorption by iron, carbon steels and stainless steels increases their corrosion rates in rather concentrated bicarbonate solutions, thus decreasing their pitting resistance [10, 11]. The effect of atomic hydrogen on the active dissolution rate of St3 in these environments is ambiguous and depends on the content of activating ions (chloride and sulfate) [11]. Adsorbed hydrogen atoms inhibit the anodic dissolution of iron in acidic sulfate solutions [12]. The purpose of this work was to study the effect of atomic hydrogen on the kinetics of active dissolution of St3 steel in electrolytes with near-neutral pH.
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