Characterization of Fe-W alloys electrodeposited from environmentally friendly electrolyte

Doctoral thesis, 2020

Nowadays, we are constantly reminded of the importance of adopting a more sustainable lifestyle. We are paying more attention on what we buy, what we eat and how we travel. We are changing our habits with the goal to lower our environmental impact and to preserve our planet. These changes are also occurring in the industrial sector where sustainable approaches are introduced in several manufacturing processes. In fact, being able to combine technological progress with environmental and sustainability measures is one of the most important challenges of our modern society. To help reaching this goal, in 2015 the United Nation proposed 17 goals for a sustainable development which represent a constant reminder of what to achieve for a better and more sustainable future. Each goal is extremely important and calls for immediate actions. Among the UN goals, the goal of a Responsible consumption and production (UN Goal number 12) represents the main guideline for industrial manufacturing processes, such as electrodeposition. Electrodeposition is a process used to deposit a layer of a desired metal from a water-based solution (electrolyte) through the application of current. Today, electrodeposition is a well-established technique used to produce coatings ranging from decorative (e.g. gold or silver for jewelry) to technological applications (e.g. chromium and nickel for anti-wear and corrosion protection). Yet, many electrodeposition processes involve the use electrolytes containing highly toxic chemicals and scarce and non-renewable resources. The European Union has recently addressed this problem with the application of environmental regulations and restrictions for the use of toxic compounds, like in the case of hexavalent chromium (i.e. Cr+6), which is classified as strongly cancerogenic. Therefore, it is important to study and develop coatings which are produced in a sustainable way. Such new coatings would be beneficial both for the environment and the electrodeposition industrial market, whose growth is limited by environmental regulations.
This thesis studies iron-based coatings which are electrodeposited using a sustainable electrolyte: minimally aggressive, thermodynamically stable, and without toxic compounds. The aim of this work is to understand how the composition of the iron-based coatings influences the microstructure and the properties of interest: mechanical, wear and corrosion properties. Heat treatments are performed to optimize both the mechanical performance and the wear resistance of the iron-based coatings, which are compared to the properties of chrome coatings. The promising results presented in this thesis represent an important step toward the application of competitive and sustainable alternatives for coatings produced by environmentally hazardous processes.