Soluble extract from Opuntia ficus-indica (Nopal extract) has been proposed in this chapter as a green inhibitor due to its component called mucilage, which has the ability to retain water; for this reason, it has been used as metal corrosion protection in machinery pieces, tools and other metallic components that need to be stored for short periods. In this way, three industrial carbon steels (AISI 1018, 1045 and 4140) have been exposed in sulfuric acid (H 2 SO 4 ) to evaluate the corrosion behavior with or without Nopal extract (NE). Some electrochemical techniques have been implemented to evaluate the corrosion inhibition efficiency (IE) such as DC linear polarization resistance (LPR) and AC electrochemical impedance spectroscopy (EIS). Results indicated a considerable superficial modification of steel in terms of dielectric constant and ion charge capacity. When the NE was added, the corrosion mechanism changed from localized to general attack, decreasing the corrosion rate in all cases. More susceptibility to fail by corrosion was observed in the 1045 carbon steel in comparison with the other two studied steels; these results were confirmed by the percentage of inhibitor's efficiency of about 95%.

Combination of good oxidation resistance, thermal stability, hardness and high strength are great interest properties in engineering and, that are possible to obtain with the Ni-Ti-B ternary system. Mechanical alloying (MA) is an alternative method and cheapest for the synthesis of this kind of metal-ceramic materials with respect to the traditional melt and quench process. The transformation sequence of all the mixtures reported the formation of (ɣ Ni) phase with a nodular morphology and identified the additional presence of the TiB 2 phase (needle morphology), which was more evident with the increase of titanium content (M2 and M3 mixtures) after 24 h of milling. Thermal activation of the milled powders showed the nucleation and growth of the Ni 3 B (O boride) and TiB 2 (Hex) as the main phases after heat treatment, where the TiB 2 phase (thin flakes morphology) was nucleated onto Ni 3 B matrix. Ternary alloy by MA took place under a metastable equilibrium, offering the possibility to form glassy alloys for compositions, which are not accessible by melting or quenching techniques.

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