Boric Acid as an Accelerator of Cerium Surface Treatment on Aluminum

Aluminum pieces are often used in various industrial processes like automotive and aerospace manufacturing, as well as in ornamental applications, so it is necessary to develop processes to protect these materials, processes that can be industrialized to protect the aluminum as well or better than chromate treatments. The purpose of this research is to evaluate boric acid as an accelerator by optimizing its concentration in cerium conversion coatings (CeCC) with 10-minute immersion time with a concentration of 0.1？g？L？1 over aluminum to protect it. The evaluation will be carried out by measuring anticorrosion properties with electrochemical techniques (polarization resistance, , polarization curves, PC, and electrochemical impedance spectroscopy, EIS) in NaCl 3.5% wt. aqueous solution and surface characterization with scanning electron microscopy (SEM). 1. Introduction Among the most striking characteristics of aluminum is its versatility, and the range of physical and mechanical properties that can be developed is remarkable. The properties of aluminum that make this metal and its alloys the most economical and attractive options for a wide variety of uses are appearance, light weight, manufacturing versatility, physical properties, mechanical properties, and corrosion resistance [1]. Aluminum and its alloys are widely used in automotive and aerospace devices. Sometimes pieces of an aircraft are submitted to aggressive environments and changes of temperature as well as condensation, resulting in corrosion attack on them. For many years, research for alternatives to chromatizing in order to diminish the damage to the environment has been carried out. Treatments that led to the development of other nontoxic coating processes with comparable adhesion properties and corrosion protection, such as conversion pretreatments formed by immersion in solutions containing phosphates, or cerium chloride, or other rare earth metal chlorides such as yttrium and lanthanum have been studied [2–5]. Approaches to cerium conversion coatings include different salts, variation on immersion temperature, anodizing, applying many layers, variation in concentration, surface activation, and use of accelerators like hydrogen peroxide [6–19]. The aim of this work is to improve understanding of accelerators on cerium conversion coatings, by studying the effect of different concentrations of boric acid as an accelerator added to CeCC at 0.1？g？L？1 at 60°C, and the role played by the substrate composition. The corrosion performance of treated aluminum surfaces that immersed 10 minutes