Scalable Corrosion-Resistant Coatings for Thermal Applications

Abstract

Corrosion of metallic substrates is a problem for a variety of applications. Corrosion can be mitigated with the use of an electrically insulating coating protecting the substrate. Thick millimetric coatings, such as paints, are generally more corrosion-resistant when compared to nanoscale coatings. However, for thermal systems, thick coatings are undesirable due to the resulting decrease in the overall heat transfer stemming from the added coating thermal resistance. Hence, the development of ultrathin (<10 μm) coatings is of great interest. Ultrathin inorganic silicon dioxide (SiO2) coatings applied by sol–gel chemistries or chemical vapor deposition, as well as organic coatings such as Parylene C, have great anticorrosion performance due to their high dielectric breakdown and low moisture permeability. However, their application to arbitrarily shaped metals is difficult or expensive. Here, we develop a sol–gel solution capable of facile and controllable dip coating on arbitrary metals, resulting in a very smooth (<5 nm roughness), thin (∼3 μm), and conformal coating of dense SiO2. To benchmark our material, we compared the corrosion performance with in-house synthesized superhydrophobic aluminum and copper samples, Parylene C-coated substrates, and smooth hydrophobic surfaces functionalized with a hydrophobic self-assembled monolayer. For comparison with state-of-the-art commercial coatings, copper substrates were coated with an organo-ceramic SiO2 layer created by an elevated temperature and atmospheric pressure metal organic chemical vapor deposition process. To characterize corrosion performance, we electrochemically investigated the corrosion resistance of all samples through potentiodynamic polarization studies and electrochemical impedance spectroscopy. To benchmark the coating durability and to demonstrate scalability, we tested internally coated copper tubes in a custom-built corrosion flow loop to simulate realistic working conditions with shear and particulate saltwater flow. The sol–gel and Parylene C coatings demonstrated a 95% decrease in corrosion rate during electrochemical tests. Copper tube weight loss was reduced by 75% for the sol–gel SiO2-coated tubes when seawater was used as the corrosive fluid in the test loop. This work not only demonstrates scalable coating methodologies for applying ultrathin anticorrosion coatings but also develops mechanistic understanding of corrosion mechanisms on a variety of functional surfaces and substrates.

Scalable Slippery Omniphobic Covalently Attached Liquid Coatings for Flow Fouling Reduction

“…The higher complexity is important to consider as the use of seawater promotes not only scale fouling but also corrosion fouling, which has been demonstrated to be significantly reduced by hybrid SOCAL coating. 35 Our work demonstrates that LIS and SLIPS suffer from lubricant drainage, with our solid-state hybrid SOCAL coating overcoming this limitation with greater long-term durability.…”

“…Corrosion resistances of the sol−gel SiO 2 and SOCAL have been studied in previous work. 35 The SOCAL coating is a few nanometers thick and the corrosion protection benefits stemming from adding the SOCAL to the sol−gel SiO 2 is negligible. However, the sol−gel SiO 2 itself is a strong barrier against flow of corrosive ions and particles.…”

“…A detailed photograph of the entire setup is shown elsewhere. 35 Each sample was immersed in the solution for 30 min, and the open-circuit potential test was carried out prior to starting the experiment. The potentiodynamic test was carried out immediately after the open-circuit potential test for each sample.…”

Novel Hydrophobic Nanostructured Antibacterial Coatings for Metallic Surface Protection

“…When compared to conventional chemical vapor deposition (CVD) of SiO 2 , which typically requires well-controlled environments, with temperatures approaching 800 • C, the sol-gel process is very advantageous, especially due to its low-temperature and atmospheric pressure. Recently, functional sol-gel-based coatings with enhanced wettability, transparency and abrasion resistance, in addition to anticorrosion properties, are a developing field of research [25]. The versatility of sol-gel approaches allows tunable chemical and mechanical properties of the protective coatings and consequently facilitates use in various application areas.…”

High Entropy Alloy Coatings and Technology

“…Thermal insulation coatings have been developed at high-temperature applications in turbine and aerospace applications. Various research activities have been conducted to improve the durability of base alloy components in various gaseous and corrosive atmospheres [3]. For example, highly oxidation-resistant coatings permit the application of various oxidizing or corrosive environments over a wider window of operating conditions.…”