Review Applications of chemometric tools in corrosion studies Giorgio Luciano, Pierluigi Traverso, Paola Letardi * CNR-ISMAR, via De Marini 6, I-16149 Genova, Italy article info Article history: Received 14 December 2009 Accepted 18 May 2010 Available online 23 May 2010 Keywords: A. Steel A. Copper alloys A. Aluminium B. Modelling studies B. Chemometrics C. Corrosion rate abstract The aim of this review is to introduce the reader to the applications of chemometric techniques in the field of corrosion science, which currently are not commonly spread. By means of key examples it will be shown how they can be fruitfully applied and enhance the quality of a laboratory workflow. Ó 2010 Elsevier Ltd. All rights reserved. 1. Introduction The following paper will briefly describe the applications of chemometric methodologies in the field of corrosion. Nowadays its use is not extensive and we will show by means of key examples how the introduction of these techniques can help in the study of this subject. Chemometrics is defined by IUPAC as the ‘‘the science of relat- ing measurements made on a chemical system or process to the state of the system via application of mathematical or statistical methods”. The word chemometrics was first coined by Wold in 1974 in the article cited in [1] and the International Chemometrics Society was formed shortly thereafter by Wold and Kowalski, two pioneers in the field. There are numerous and different groups of people interested in chemometrics that gravitate in different fields of chemistry. The potential for application is huge, since a good laboratory practice would always be able to apply correct statistics to the experiments planned and performed. Chemometrics is currently applied in the field of physical chem- istry (kinetics and equilibria study), organic chemistry (reaction optimisation), theoretical chemistry and also chromatography and spectroscopy and subsequently every application involved with these techniques such as environmental monitoring, indus- trial process monitoring, biology, forensic science, etc. [2]. The most used methodologies applied in the field of chemomet- rics are: (1) Signal processing, (2) Design of Experiments (DoE) and response surface modelling, (3) Pattern recognition, (4) Calibration. Some key examples of applications to corrosion studies will be described in order to enlighten the advantages in applying such techniques. We have preferred to focus on DoE, pattern recognition and calibration only, since the available literature in the field of signal processing is wide and established and also a small overview would have been overwhelming [3]. 2. Design of Experiments (DoE) In classical research methods, the main objective is to define the rule/law, which has the property of an absolute category, at a given level of knowledge in other words the law is either unconditionally correct or not. When we have to deal with a complex system this kind of approach becomes difficult to apply because when many factors have complex effects it is difficult to find the correct math- ematical system in agreement with the laws. The essence of DoE is that it enables optimal solutions to be obtained even when it is really impossible to get a functional (deterministic) mathematical model and define a rule precisely. In DoE we use polynomial models since the quality of approxi- mation may be improved by increasing a polynomial degree. Such 0010-938X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.corsci.2010.05.016 * Corresponding author. Tel.: +39 0106475434. E-mail address: paola.letardi@ismar.cnr.it (P. Letardi). Corrosion Science 52 (2010) 2750–2757 Contents lists available at ScienceDirect Corrosion Science journal homepage: www.elsevier.com/locate/corsci