Dynamics of scaling and corrosion in the natural environment: the long-term sustainability of geothermal energy technologies through exp

碳钢的二氧化碳(CO2)腐蚀是一种退化机制，以其在能源部门，特别是地热能源生产中的表现而闻名。尽管进行了广泛的研究，但二氧化碳腐蚀过程的复杂性仍然没有解决真正的反应途径，特别是腐蚀产物的增长和局部腐蚀机制的问题。尽管人们在加强对CO2腐蚀机理的理解方面进行了广泛的研究，并开发了大量的预测腐蚀模型，但在文献关注方面仍存在明显的差距。大部分工作是为了了解和预测在没有保护性腐蚀产物的情况下的均匀腐蚀，而对存在这种表面沉积物的局部腐蚀的关注较少。一方面，这可能令人惊讶，因为局部腐蚀是能源行业最大的失效模式之一。然而，碳钢等活性材料的局部腐蚀机制似乎特别难以阐明和缓解。与被动材料中的局部腐蚀相比，这种过程几乎没有被很好地理解或描述，后者的机制通常被很好地建立和接受。对于碳钢在含CO2环境中的局部腐蚀，已有大量的理论和影响参数被赋予。许多建议都围绕着局部非均质性的存在或产生，无论是表面化学还是表面结构/成分，这总是促进电偶/浓集电池或有助于诱导酸化过程，从而加剧离散地区的腐蚀。一个被认为是局部腐蚀的前兆的因素是与钢表面碳酸盐(FexCayCO3)腐蚀产物的沉淀有关的因素。当在适当的条件下形成时，这种涂层可以高度保护不受一般和局部腐蚀，在实验室研究中将腐蚀速度抑制高达两个数量级。这是通过层作为电化学活性物种的扩散屏障和/或阻止钢表面上的活性位置来实现的。尽管腐蚀产品有明显的好处，但许多作者认为，这些层的零星、不均匀的覆盖不利于管道的完整性，因为它有利于局部腐蚀的开始和传播。事实上，一些研究论文提到局部腐蚀的潜在机制与局部去除腐蚀产物有关。虽然这可能是真的，但这一说法有一些错综复杂之处，应当加以探讨，以便充分了解这种机制的启动情况，并考虑可能的替代理论/解释。应了解腐蚀沉积物下或存在部分覆盖的系统中局部腐蚀的实际驱动因素，以便全面了解此类系统中的不同腐蚀模式、步骤和机理。只有了解所有的可能性、它们的复杂性和这些反应的驱动因素，才能有效地控制这些过程，以防止失败。

Carbon dioxide (CO2) corrosion of carbon steel is a degradation mechanism known for its manifestation within the energy sector, particularly in the geothermal energy production. Despite extensive research, the complexities of CO2 corrosion processes has still left aspects regarding the true reaction pathways and, in particular, corrosion product growth and localised corrosion mechanisms, unresolved. Despite widespread research efforts related to enhancing the understanding of CO2 corrosion mechanism, as well as the development of a plethora of predictive corrosion models, there is a clear disparity in literature focus. The majority of effort is directed towards understanding and predicting uniform corrosion in the absence of protective corrosion products, with less attention afforded to localised corrosion in the presence of such surface deposits. On the one hand, this may be surprising given that localised corrosion constitutes one of the greatest failure modes within the energy sector. However, the localised corrosion mechanism in active materials such as carbon steel appears to be particularly difficult to both elucidate and mitigate. Such processes are not nearly as well understood or characterised compared to localised corrosion in passive materials, where the mechanisms are generally well established and accepted. Numerous theories and influential parameters have been assigned to localised corrosion of carbon steel in CO2-containing environments. Many of those proposed revolve around the existence or generation of local heterogeneity in terms of either surface chemistry or surface texture/composition which invariably promotes galvanic/concentration cells or aids in inducing acidification processes which accentuate corrosion in discrete areas.One factor which has been identified as a pre-cursor to localised corrosion is that associated with the precipitation of carbonate (FexCayCO3) corrosion products on steel surfaces. Such layers can be highly protective against general and localised corrosion when formed under appropriate conditions, suppressing corrosion rate by up to two orders of magnitude in laboratory studies. This is achieved through the layer acting as a diffusion barrier to electrochemically active species and/or blocking active sites on the steel surface. Despite the clear benefits of corrosion products, many authors have suggested that the sporadic, non-uniform coverage of such layers is detrimental to pipeline integrity, as it is conducive to both the initiation and propagation of localised corrosion. In fact, a number of research papers refer to the underlying mechanisms of localised corrosion being associated with the local removal of corrosion products. Whilst this may be true, there are some intricacies associated with this statement which should be explored to gain a full appreciation of the initiation of such mechanisms, as well as consideration of possible alternative theories/explanations. The actual driver for localised corrosion in systems under corrosion deposits or where there is partial coverage should be understood in order to have a full appreciation of the different modes, steps and mechanism of corrosion in such systems. Only by having an understanding of all eventualities, their complexities and the drivers for such reactions can these processes be effectively controlled to prevent failures.