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1. Introduction
Copper and copper-based alloys are widely used in a great variety of applications, such as heat exchangers, building construction, electronics, coinage, art works, cultural objects and statues (Zhang et al., 2003). However, when they are exposed to an urban polluted environment such as acid rain, bells, statues and all copper-based alloys suffer from an acceleration of the corrosion phenomena that occur in their surfaces (Bostan et al., 2012; Dermaj et al., 2007; Picciochi et al., 2004; De Cristofaro et al., 2012; Chen et al., 2015; Zohdy et al., 2014; Sidot et al., 2006; Milosev et al., 2010; Bernardi et al., 2009, Brunoro et al., 2003; Muresan et al., 2007; Laguzzi and Luvidi, 2010; Morselli et al., 2004). One practice very often used to prevent copper alloys corrosion is the use of corrosion inhibitors, most of the times organic compounds which contain heteroatoms in their structure such as sulfur, nitrogen and oxygen (Varvara et al., 2008; Marusic et al., 2011; Nazeer et al., 2014; Wang et al., 2013; Rahmouni et al., 2009; Balbo et al., 2012; Wang et al., 2004; Zhang et al., 2004; Khaled et al., 2004; El-Sayed, 2006). However, even when these synthetic compounds are very effective in controlling corrosion processes, their production is very expensive, and they can be very toxic and hazardous toward environment and human being, limiting its use. In the past decades, plant extracts that contain compounds with nitrogen, sulfur and oxygen have been used as naturally occurring corrosion inhibitors which are much less toxic, inexpensive and readily available (Khan et al., 2015; Fouda et al., 2015; Raja et al., 2013; Lake, 1988; El-Etre, 2007; Umoren et al., 2015; Okafor et al., 2007; El-Etre et al., 2005; Ramde et al., 2014; Radojčić et al., 2008). Salvia hispanica (S. hispanica) is a seed that is widely used in Mexico for medicine, food and oil (Bushway et al., 1981). Among its main compounds are linoleic and α-linolenic acids (omega-3 and omega 6), myrcetin, quercetin, kaempherol and caffeic acid (Heuer et al., 2002), all of them with...