Effects of Surface Morphology on Erosion–Corrosion and Corrosion Resistance of Highly Hydrophobic Nickel-Tungsten Electrodeposited Film

Parinaz Salehikahrizsangi,Keyvan Raeissi,Luigi Calabrese,Fathallah Karimzadeh,Edoardo Proverbio

doi:10.3390/coatings11091084

Parinaz Salehikahrizsangi, Keyvan Raeissi + Show 3 more

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https://doi.org/10.3390/coatings11091084

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Journal: Coatings	Publication Date: Sep 7, 2021
Citations: 5	License type: CC BY 4.0

Affiliation: Isfahan University of Technology, University of Messina

Abstract

Hard nanocrystalline Ni-Co or Ni-W coatings are receiving a growing interest owing to their premium hardness, wear, and corrosion properties for several industrial applications. Furthermore, surface hydrophobicity greatly improves surface corrosion resistance. In this research, the durability of hydrophobic hierarchical NiW electrodeposited film has been evaluated in a high-speed slurry erosion–corrosion (EC) test rig. Two different coatings have been tested: a rough coating obtained in a chloride-based bath (NiWchloride) and a smooth coating obtained in a sulfate-based bath (NiWsulfate). Corrosion behavior over time was evaluated by electrochemical impedance spectroscopy (EIS), while surface hydrophobic performance was determined by the sessile drop method. The morphological features of the coatings were assessed by scanning electron microscopy while roughness modification during the EC tests were identified by means of an atomic force microscopy. During static immersion in the aggressive solution, the impedance modulus of the coatings continuously increased due to an increase in the thickness of corrosion products. During the EC test, the impedance modulus of the smooth NiW coating decreased, losing its barrier property. It was observed that the increase in impedance modulus of the hierarchical structure of the rough NiW coating during EC was far greater than that during static immersion. After 64 min of EC, the NiWchloride was able to resume its hydrophobicity property by storing in air; nevertheless, the NiWsulfate, with a loss of approximately 72% in its initial contact angle, was no longer hydrophobic. The results showed improvements in the lifetime of hydrophobic NiW coatings in erosion–corrosion conditions of the hierarchical nanostructure obtained in a chloride-based electroplating bath.

Highlights

In recent years, nanocrystalline nickel alloy coatings (e.g., Ni-W, Ni-Co) have received growing interest as an efficient replacement for hard chromium coatings for their superior hardness, wear, and corrosion properties for several applications, from microelectronics to mechanics [1,2]
An increasing number of research activities have focused on the corrosion resistance improvement of these coatings by promoting surface hydrophobicity to gain better performance in critical environmental conditions such as marine environments [3,4]
Even with effective corrosion protection, the marine components may still suffer due to relatively low erosion resistance [15]

Summary

Introduction

Nanocrystalline nickel alloy coatings (e.g., Ni-W, Ni-Co) have received growing interest as an efficient replacement for hard chromium coatings for their superior hardness, wear, and corrosion properties for several applications, from microelectronics to mechanics [1,2]. The driving force of this concept is to obtain water repellent metal surfaces and modify the anti-corrosion surface capabilities of metals and alloys, slowing down the breakage of the metal oxide film and preserving the metal substrate from undesired localized corrosion attack [5] In such a context, research advances in bio-inspired non-wetting surfaces have been recently developed, focusing attention on water repellent surfaces with a specific hierarchical (multi-scale) rough structure [6,7,8,9]. The corrosion resistance mechanism functions as follows: when exposed to an aggressive environment, the hydrophobic coatings, characterized by rough and regular hierarchical structures, can trap a significant amount of air within the valleys and cavities of the hierarchical surface profile [10,11]. The development of hydrophobic coatings with improved erosion–corrosion resistance is a matter of interest, since the low durability and stability of the hierarchical structured surfaces to the EC condition is a relevant issue that limits their practical usability in the industrial field [16,17,18,19]

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