Durability of Lubricated Icephobic Coatings under Various Environmental Stresses

Icephobic coatings interest various industries facing icing problems. However, their durability represents a current limitation in real applications. Therefore, understanding the degradation of coatings under various environmental stresses is necessary for further coating development. Here, lubricated icephobic coatings were fabricated using a flame spray method with hybrid feedstock injection. Low-density polyethylene represented the main coating component. Two additives, namely fully hydrogenated cottonseed oil and paraffinic wax, were added to the coating structure to enhance coating icephobicity. Coating properties were characterised, including topography, surface roughness, thermal properties, wettability, and icephobicity. Moreover, their performance was investigated under various environmental stresses, such as repeated icing/deicing cycles, immersion in corrosive media, and exposure to ultraviolet (UV) irradiation. According to the results, all coatings exhibited medium-low ice adhesion, with slightly more stable icephobic behaviour for cottonseed oil-based coatings over the icing/deicing cycles. Surface roughness slightly increased, and wetting performances decreased after the cyclic tests, but chemical changes were not revealed. Moreover, coatings demonstrated good chemical resistance in selected corrosive media, with better performance for paraffin-based coatings. However, a slight decrease in hydrophobicity was detected due to surface structural changes. Finally, paraffin-based coatings showed better resistance under UV irradiation based on carbonyl index and colour change measurements.

Innovative Study on Microstructural Change in Duplex Stainless Steel in Corrosive Media

Duplex Stainless Steel was developed long back in 1930 and gradually finds its wide application because of its high strength, good weldability, good toughness and resistance to stress corrosion cracking. This alloy finds its application in pressure vessels, bridges, process plants and also in typically down to minus 50 degree centigrade applications. However, because of its high alloy content thermal conductivities of duplex stainless steel are low. Casting this alloy is difficult and can be industrially used after proper heat treatment. In this present study corrosion rates were measured for CD4MCu in terms of weight loss/unit area/hour and microstructures were observed in different corrosive medium with time as variable.

Dimensional Stability of Low Temperature Surface Hardened Stainless Steel Components*

Stainless steels are commonly used for high precision components, which often are exposed to corrosive media. However, their inferior tribological behaviour restrict the use of these materials in many technical applications. Thermochemical surface hardening is one way to overcome these weaknesses. Solution nitriding in the austenitic range above 1000 °C is mainly used for hardening martensitic and ferritic stainless grades. In austenitic and duplex stainless grades, however, the hardening effect is limited. Additionally, the high process temperatures combined with a necessary rapid cooling may lead to non-desired dimensional changes. Low temperature surface hardening processing below 500 °C here offers interesting alternatives for increasing the wear properties, while maintaining the corrosion resistance. This paper demonstrates the influence of high and low process temperatures of thermochemical surface hardening treatments on the tight dimensional tolerances of a rotationally symmetrical precision component made from cold worked AISI 304. Based on these results, current and new industrial applications, which benefit from low temperature surface hardening, will be discussed.

Study of Ti – Al based high-temperature cermet filters

Operation in corrosive media and/or at high temperatures requires improved characteristics of the performance and durability of filtering equipment. The Ti – Al intermetallic system combines low density with high strength and exhibits high resistance to oxidation and corrosion at elevated temperatures. We present the results of studying high-temperature Ti – Al cermet products (filters) with nanoscale pores. Filters were obtained from a mixture of Ti and Al powders (mass ratio 40:60) by thermal explosion. XRD methods showed that the synthesized material consists of two main phases: TiAl3 and Al2O3. The microstructure analysis revealed the presence of large-sized TiAl3 structures and spherical Al2O3 aggregates enveloped by nanostructured TiAl3. Moreover, nanoscale fibrous TiAl3 compounds forming a multilevel developed cobweb-like structure are observed in the entire volume of the pore space of the material. The open porosity of the material was 48%, the pore size was 0.1 – 0.2 μm, the efficiency of the porous material was 99.999%, the resistance to gas flow was 100 mm of water column, and the filtration index was 0.062. Thermal tests revealed the possibility of effective use of filters under conditions of elevated (up to 800°C) temperatures and corrosive media due to the chemically stable and heat-resistant binary structure of the material. The results obtained can be used to improve the methodology of the development and operation of high-temperature cermet filters based on Ti – Al.

High-Temperature Corrosion Performance of FeAl-Based Alloys Containing Carbon in Molten Salt

Corrosion behavior of FeAl-based alloys containing carbon produced through arc melting in argon atmosphere has been studied at 500 °C to 700 °C. The samples were tested in the aggressive environment of molten salts (80%V2O5/20%Na2SO4). The corrosion behavior was observed by weight change method and the layer products formed were examined by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The different phase components were observed in the surface layer after the test in Fe-22Al alloy. A protective Al2O3 layer was confirmed for Fe-22Al alloy containing carbon only. However, an additional TiO layer was also observed in Fe-22Al alloy containing carbon with Ti addition. The microstructural and XRD examinations revealed that this additional TiO layer protects better against penetration of corrosive media. The corrosion resistance behavior of FeAl-based alloys were addressed on the basis of microstructural evidence.

Galvanic Corrosion Behaviour of Different Types of Coatings Used in Safety Systems Manufacturing

Worker safety is one of the main aspects to be taken into account in any activity carried out at work. When we talk about the safety of the worker at activities carried out at height, the condition and characteristics of the personal protective equipment against falling from a height are one of the main causes of work accidents resulting in serious injuries or death. Carabiners are the main components of the safety system; their role is to connect the other components of the system or to make the connection between the system and the anchor point. Therefore, to be used safely, the carabiners’ material must have high corrosion resistance in different environments. This paper is part of a complex study that aims to improve the corrosion properties of carbon steel used in the manufacture of carabiners. Previous studies have shown that the corrosion resistance of carbon steel in various corrosive environments has been improved by the deposition of different types of phosphate layers, as well as other subsequently deposited layers. The aim of this paper is to study the galvanic corrosion evaluation between different galvanic couples (duralumin-coated samples, aluminium bronze-coated samples, and carbon steel-coated samples) tested in three different corrosive media. Moreover, the study approaches for the first time the galvanic corrosion of systems that can be formed between the materials used in the manufacture of carabiners. Accordingly, it was observed that, overall, the samples coated with a Zn phosphate layer exhibited the best performance in all the corrosive environments (saltwater and fire extinguishing solution).

A review on the corrosion resistance of electroless Ni-P based composite coatings and electrochemical corrosion testing methods

This paper aims to review the impact of different factors influencing the corrosion resistance of electroless Ni-P based coatings. Emphasis has been given onto the impact of phosphorus content, incorporation of alloying elements, addition of particles and heat treatment which have been discussed in detail and critically reviewed. The effect of corrosive media and coating process parameters on corrosion resistance are studied concisely. Furthermore, the role of the incorporation of various elements and particles’ contents on the corrosion resistance of electroless Ni-P coating are studied systematically. This paper also presents an overview of the latest electrochemical corrosion measuring techniques. The following approaches deserve special attention in the analysis: localized electrochemical impedance spectroscopy (LEIS), scanning vibrating electrode technique (SVET), scanning ion-selective electrode technique (SIET), scanning droplet cell (SDC), scanning electrochemical microscopy (SECM), scanning Kelvin probe (SKP) and novel contactless technique (NCT).