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Recent Developments in Waterborne Polyurethanes for Corrosion Protection
Published in Ram K. Gupta, Ajay Kumar Mishra, Eco-Friendly Waterborne Polyurethanes, 2022
Felipe M. de Souza, Muhammad Rizwan Sulaiman, Ram K. Gupta
Corrosion inhibitors can be categorized into two main groups: organic and inorganic inhibitors. The inorganic inhibitors are further classified into anodic and cathodic inhibitors. Besides these inhibitors, some inhibitors change the surroundings to restrict corrosion. These inhibitors are called environmental conditioners, which can also be categorized into scavengers and biocide inhibitors [1]. The anodic inhibitors are metal oxides covering the anode metal produced by chemical reaction or undergo natural oxidation with air. The oxide layer formed naturally is known as the native oxide layer, which prevents corrosion due to its inactive character [2]. Various metals, such as Al, Zn, Mg, Cu, Cd, Ti, Ag, Si (semi-metal), and Sn, can undergo passivation with their corresponding oxides. The oxide covering is typically in the range of a few nanometers for efficient protection. The oxide covering thickness plays a vital role in productive corrosion protection. If the thickness is more than required, the coating can get cracked and may get inefficient potection [2]. However, the employment of surface passivating materials has also been done for various implementations. These include the passivation of titanium-based materials with zinc alloys utilized in semiconductors, aluminum oxides with silicon-containing covering in solar cells, and application of the dielectric coating in electronic components.
Chips with Everything
Published in Sharon Ann Holgate, Understanding Solid State Physics, 2021
This insulation is, of course, essential. Without insulators we would not be shielded from the harmful currents carried by any electrical cables—from the massive power lines of electrical grids to the much smaller wires that supply electricity to household devices like kettles and televisions. Meanwhile, semiconductor devices and integrated circuits would be useless without the insulating materials in between the conducting channels that stop them from touching one another and so prevent short-circuiting. Many devices also contain dielectric layers that provide electrical insulation between conducting layers. In addition, dielectrics are used as masks during doping (see Section 7.3.5) and for passivation. Passivation is the protection of electronic components and circuits from moisture, scratching, and impurities. The surfaces of most silicon chips, for example, will be covered with a layer of silicon dioxide (SiO2) or silicon nitride (SiN), which helps protect them from harmful environmental conditions such as a humid atmosphere.
Open-Circuit Metal Dissolution Processes
Published in Madhav Datta, Electrodissolution Processes, 2020
The CMP slurry consists of abrasives and chemicals that are homogenously suspended in water. During CMP, the slurry is spread over the pad. The slurry continuously delivers the chemical components and abrasive particles to the entire wafer. The material removal in CMP is the result of an interaction between chemical and mechanical forces. Material removal occurs when the rotating wafer surface is pushed against a soft polymer pad attached to the rotating platen in the flooded slurry. The wafer is mounted upside down on a backing film in a rotating carrier, and a diamond conditioner is used to dress the pad to maintain its surface roughness during polishing. The CMP slurry consists of abrasives and chemicals that are homogenously suspended in water. A chemically reacted layer forms by a chemical reaction between wafer and slurry, which is removed by the mechanical abrasion. The passivation layer is a chemically reacted layer, such as a stabilized oxide on the surface, which protects the final surface from corrosion. The removal mechanism of metal CPM is the repetition of generating a passivation film and its removal by mechanical abrasion [25].
Effect of Ti on the corrosion behaviour of as-cast Fe–17Cr ferritic stainless steel
Published in Corrosion Engineering, Science and Technology, 2021
Junwei Fu, Kai Cui, Feng Li, Yucheng Wu
The change in ND and NA values is usually due to non-stoichiometric defects of the space charge layer or disorder and impurity concentration of the passivation film. The values of ND and NA have an important influence on the corrosion resistance of the samples. If the value of ND and NA is smaller, the point defects in the passivation film are less. Thus, the formed passivation film is more stable and less prone to decomposition, and the corrosion resistance is better. The parity potential EFB indicates the electrical properties of the passivation film where the sample exhibits semiconductor characteristics.
Influence of the post-processing operations on surface integrity of metal components produced by laser powder bed fusion additive manufacturing: a review
Published in Machining Science and Technology, 2020
Hamaid Mahmood Khan, Yusuf Karabulut, Ozhan Kitay, Yusuf Kaynak, I. S. Jawahir
The surface roughness with irregular peaks and troughs were found significant in escalating corrosion characteristics. The smooth surface profiles in conventional products were reported having comparatively higher pitting potential that reduces the probability of the formation of the pit, thereby enhancing the corrosion resistance significantly (Hong and Nagumo, 1997). However, on the other hand, the lower pitting potential and high discharge current density were recorded in LPBF structures because of the high surface roughness and unstable metal oxide layers (Dai et al., 2016a). The poor stability of passive layers on rough surfaces intensifies the metal degradation inside the troughs and also reduces the re-passivation potential. The passivation process involves the removal of free ions formed on the surface or inside the pits after the initial occurrence of pitting corrosion. The passivation can be self-passivating or can be applied externally to protect the surfaces against the corrosion. The formation of a passive layer and its morphology determines the protection level of the underlying material. Thus, effective passivation protects the surface of the material from further corrosion attacks. However, re-passivation potential in LPBF structures is observed quite low in comparison to conventional products because of the large concentration of pores and surface imperfections. These inhibitions further aggravate the corrosion rate and may delay the self-sustainability of the passive layers on the surfaces of the as-built LPBF structures. In addition to this, the pore size also significantly influence the corrosion behavior where the large and irregular pores above 40 µm were found more prone to corrosion attack (Kong et al., 2018a).