Inhibitor Coatings against High Temperature Corrosion

本提案的主要目标是详细阐述所描述的新型涂层方法，该方法可以防止在陆地，海洋和航空涡轮发动机以及燃烧低质量燃料的化学过程中经常观察到的高温沉积腐蚀。提出的新型缓蚀剂涂层应通过纳米或微米级颗粒改性扩散涂层来获得。所追求的涂层将包括典型扩散涂层的基体，如铝化物，其中抑制剂或盐介质颗粒或两者的组合是随机分布的。这种涂层的优点是，当硫酸盐或钒酸盐等腐蚀性物质溶解原本具有保护作用的氧化铝垢时，盐就会与添加的颗粒接触。缓蚀剂颗粒将被牺牲以形成高熔点，或者酸度的变化将减缓腐蚀，使熔体的侵蚀性降低。主要目的是通过研究涂层的效率、耐化学性以及潜在的腐蚀机制来测试这种新方法。作为参考，将使用由低活性包胶结制造的工业最先进的非改性扩散涂层。涂层将暴露在两种盐层下，这两种盐层分别代表钒酸盐增强（60%V2O5-40%Na2SO4盐）和经典的Na2SO4 II型腐蚀，最长可达1000h。此外，将进行循环氧化试验，以验证修改本身是否会影响寿命，例如，通过诱导裂纹。将对不同试验的不同短期、中期和长期（长达1000小时）暴露样品进行详细调查。

The main goal of the present proposal is to elaborate the described novel coating approach, which can prevent the deposit corrosion at high temperatures often observed in land, marine, and aero turbine engines and chemical processes firing low quality fuels. The novel, proposed inhibitor coating should be obtained by modifying diffusion coatings with nano- or microscale particles. The pursued coatings will consist of a matrix of a typical diffusion coating such as aluminide in which inhibitor or salt mediating particles or combinations of both particles are randomly distributed. The advantage of such coatings is that, when corrosive substances such as sulphates or vanadates dissolve the otherwise protective alumina scale, the salt comes in contact with the added particles. The inhibitor particles will be sacrificed to form high-melting species or the corrosion will be retarded by a change in the acidity, making the melt less aggressive. The major objective is to test this new approach by investigating the efficiency of the coating and its chemical resistance as well as the underlying corrosion mechanisms. As a reference, an industrial state of the art, non-modified diffusion coating manufactured by low activity pack cementation will be used. The coatings will be exposed under two salt deposits that represent vanadate-enhanced (60%V2O5-40%Na2SO4 salt) and classical Na2SO4 type II corrosion for up to 1000h. In addition, cyclic oxidation tests will be performed to validate if the modifications themselves would affect the lifetime, e.g. by inducing cracks. Detailed investigation of the different short-, medium-, and long-term (up to 1000h) exposed samples of the different tests will be carried out.