Electrochimica Acta 58 (2011) 322–329 Contents lists available at SciVerse ScienceDirect Electrochimica Acta j ourna l ho me pag e: www.elsevier.com/locate/electacta Dissolution and passive film formation of Sn and Sn coated steel using atomic emission spectroelectrochemistry L. Jiang a , P. Volovitch a , U. Sundermeier b , M. Wolpers b , K. Ogle a,∗ a Chimie-ParisTech, ENSCP, UMR7045, 11 rue Pierre et Marie Curie, Paris 75005, France b Henkel AG & Co. KGaA, Adhesive Technologies, 67 Henkelstraße, 40191, Düsseldorf, Germany a r t i c l e i n f o Article history: Received 7 June 2011 Received in revised form 18 September 2011 Accepted 19 September 2011 Available online 29 September 2011 Keywords: Anodization Passivation Tin Spectroelectrochemistry Corrosion a b s t r a c t Atomic emission spectroelectrochemistry (AESEC) was used to quantify simultaneously the rates of Sn dissolution and SnO 2 film formation for Sn and Sn coated steel in carbonate solution at pH 11.2. The technique is demonstrated by applying different potentiostatic treatments (variable potential and time) and measuring the amount of oxide formed and Sn dissolved during the treatment, and subsequently measuring the open circuit dissolution rate following the treatment. It is observed that the degree of passivation is a strong function of potential and time. Cathodic and low potential anodic potentiostatic treatments lead to a dissolution–precipitation mechanism that does not significantly passivate the sur- face. The stability of the passive film was investigated as a function of the quantity of oxide generated. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Tin coatings on steel are frequently used in the food and elec- tronic industry because tin is nontoxic, ductile and easy to solder. When exposed to the atmosphere, a tin oxide film is formed on the surface that reduces the corrosion rate to moderate levels, enhances polymer adhesion, and reduces tarnishing. For many applications, however, the oxide film does not give sufficient corrosion protec- tion and a supplementary passivation step is required [1]. The state of the art passivation methodology in use today involves forming a Cr(III) hydroxide film using a secondary chromate post-rinse [2]. This may be done using either electrodeposition to reduce Cr(VI) to Cr(III) and Cr(0), or alternatively, by simple exposure to a chro- mate solution followed by a rinse with a citric acid or gluconic acid solution to reduce excess Cr(VI) to Cr(III). In recent years the search for non chromate based passivation treatments has become fash- ionable and the idea of simply reinforcing the native SnO 2 film by electlectrochemical anodization has regained interest [3] although the method is quite old with the earliest patents dating back to the 1930s [4]. In particular, carbonate solutions are among the most commonly used electrolytes for this application [5–7]. An extensive literature exists on the kinetics of tin passivation and the nature of the passive film and Ref. [8] gives a fairly thor- ough review up to 1989. The basic structure of the passive film in ∗ Corresponding author. E-mail address: kevin-ogle@enscp.fr (K. Ogle). alkaline solution was proposed by Kapusta and Hackerman [9] and confirmed by subsequent authors. In alkaline solution, it is well established that the oxide film consists primarily of SnO 2 when formed at high anodic potentials although a thin layer of SnO has been detected at the interface Sn/oxide [10,11]. The ratio of Sn(IV) to Sn(II) increases markedly as the anodization potential becomes higher; and at more negative potentials it is thought that a SnO or Sn(OH) 2 film dominates, most likely formed through a disso- lution precipitation mechanism [12]. The amorphous Sn(OH) 2 and Sn(OH) 4 films have been described as a “prepassive” film. The final- ized passive film is formed when Sn(II) is oxidized to Sn(IV) and the hydroxide species are dehydrated to the oxide [13]. Despite the extensive literature and kinetic models based on film growth and dissolution, to our knowledge, the relationship between the state of the passive film and the dissolution rate of the underlying substrate has never been determined experimen- tally due to the difficulty of measuring simultaneous dissolution and film formation. This is an important omission in that the ulti- mate goal of a passivation treatment on a plating line is to reduce the corrosion rate. Further, due to high line speeds (up to 3 m/s) the passivation treatment must be obtained in a very short time period, on the order of seconds, and under conditions which may not be optimum for passivation. In this work, we aim to measure the total electrical current and the dissolution rate of Sn independently during and after electrochemical treatment of the Sn. This allows us to measure the effect of the electrochemical treatment on the subsequent Sn dissolution rate. Further, this methodology permits an improved quantitative estimate of the amount of oxide on the 0013-4686/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2011.09.046