New strategies to control the effects of corrosion on metallic materials

Organised by the AZTERLAN Metallurgy Research Centre and the TABIRA Foundry Institute with the support of SOCIEMAT and the European Corrosion Federation, the webinar “Strategies to mitigate the effects of corrosion on metals in corrosive environments” gathered 80 technicians and specialists to share experiences and new technological developments in the field of corrosion of metallic materials.

In the fight against corrosion, research and new technological developments are oriented towards minimising the effects of this phenomenon on materials, components and structures, while seeking to delay its “inevitable appearance”. The most common research lines in this field focus on the understanding of the corrosion mechanisms (types of corrosion), on materials protection systems (coatings, design of advanced alloys, … etc.) and on the environment where the material is exposed to and interacts with.

This outstanding technical framework allowed to share innovations and new developments from the companies METROHM HISPANIA and MESHIND, as well as AZTERLAN Technology Center, aimed at delaying the appearance of corrosion and mitigating its effects.

The session began with the lecture of METROHM HISPANIA, represented by Jesús García de la Fuente. Mr. García illustrated the audience about the characteristics and opportunities offered by electrochemical testing to evaluate the properties of metallic materials against corrosion. “Corrosion is the result of an electrochemical reaction between metal and the elements in contact. For this reason, electrochemical tests are an important source of information when assessing the characteristics of materials and their behaviour”. In his presentation, Mr. García shared the most common electrochemical methods applied on the main problems that the metal-mechanical industry must deal with.

Organizers and speakers share their experiences and case studies to mitigate the effects of corrosion

Regarding these testing techniques, the METROHM HISPANIA expert indicated that they are “standardised methods” that comply with the specifications of international standards related to corrosion, emphasizing their complementarity with other testing methods, and highlighting time saving as their main advantage. “In a few hours, electrochemical tests can offer results that other methods, such as salt spray, can take days or weeks”. However, he also clarified that these results cannot substitute or equate each other and that “they are used mainly to verify and ensure the characteristics of the materials”.

The next presentation was shared by Mrs. Enara Mardaras, AZTERLANŽs researcher specialized in corrosion and protection of metallic materials, focused on the research carried out to deliberately provoke a mold-metal reaction to improve the surface layer of cast components. As explained by Mrs. Mardaras, this work has allowed “to conclude that the surface modification of casting components by means of the diffusion of specific alloying elements is a possible option to achieve surface structures with improved properties”.

Mrs. Mardaras presented to the audience two cases of surface modifications carried out using FeCr and stainless-steel duplex powder. “Although in both cases a higher surface hardness and a greater resistance to wear has been achieved, only the duplex surface modification has presented improved properties against corrosion”.

Regarding the industrial application of the conclusions of the research work, the corrosion expert indicated that “this experience can be reproduced on an industrial scale, although a personalized previous study is required to analyse the characteristics of the material, the geometry of the components to be manufactured and the specific characteristics of the whole production process”.

The third technical lecture of the day was brought by Unai Garate, Manager of the New Technology-Based Company MESHIND (Metal Stamping & Hot Industry S.L.), dedicated to the development and application of ad-hoc metal coatings by means of laser cladding technologies (LMD). This technology “allows to apply coatings that provide advanced mechanical properties in active surface areas of metallic components, which can be deposited in a simpler base material”. Resistance to corrosion is one of the properties that we can be conferred to these components.

The recharging of materials by LMD to provide components greater corrosion protection can be used, for example, in “products carrying corrosive media that are manufactured in corrosion-resistant alloys or in applications where a precise control of the material added for higher performance in service is required”. In each scenario, the aim of laser metal cladding is different, being able to go “from the modification of the chemical composition or the application of heat treatments in a very localised way, to adding the strictly necessary metal to guarantee anti-corrosion requirements”.

In the words of Mr. Garate, the key for the proper application of this technology is that the development of the material to be added and the development of the LMD process parameters must go hand in hand. Otherwise, “the outcome could be critical”.

The session came to an end with the participation of the coordinator of Failure Analysis and Diagnosis Department of AZTERLAN, Mr. José Antonio Goñi, who focused his presentation on the main pathologies caused by corrosion. “Corrosion is a phenomenon that presents significant particularities and difficulties, because even though it is the result of the chemical interaction between the material and the medium, it can come accompanied by other factors, such as mechanical loads”.

“When we analyse the mechanisms of corrosion failure, we usually put on the table a more critical view than usual:  Why shouldn’t this component have corroded? “. Thus, the search of the origin of the failure is directed towards the “identification of the failure mechanisms or towards those elements that indicate that the material has not behaved as it should have, trying to determine the causes”. As for corrosion failures, “the question is not whether a material can corrode or not; corrosion is an inevitable phenomenon. The question that should be asked is why it will suffer corrosion, which kind of corrosion will happen, how will corrosion impact the functionality of the component or material and when will corrosion appear. If the how and when do not fit the expectations, this is where we should act.”

The expert in failure analysis ended his conference by sharing with the audience some case studies of premature failures caused by different types of corrosion, as well as the most common causes and factors behind them.

Framed within “Corrosion Awareness Day 2021”

This technical event joins the celebrations of Corrosion Awareness Day, the international day to raise awareness of the social, economic, and environmental effects of this phenomenon. As organizers of the technical meeting, AZTERLAN Research Center and the TABIRA Foundry Institute have made a “very positive” evaluation of the technical level and the interest generated by this outstanding technical framework.

“This initiative has captured the interest of the industry and the participation of technicians from companies has been remarkable. This shows the concern for this phenomenon, which undoubtedly affects all sectors involved in the use of metallic materials.”