Purpose: The purpose of this paper is to review and examine three of the most common corrosion characterization techniques specifically on Sn-Zn solders. The discussion will highlight the configurations and recent developments on each of the compiled characterization techniques of potentiodynamic polarization, potentiostatic polarization and electrochemical impedance spectroscopy (EIS).Design/methodology/approach: The approach will incorporate a literature review of previous works related to the experimental setups and common parameters.Findings: The potentiostatic polarization, potentiodynamic polarization and EIS were found to provide crucial and vital information on the corrosion properties of Sn-Zn solders. Accordingly, this solder relies heavily on the amount of Zn available because of the inability to produce the intermetallic compound in between the elements. Further, the excellent mechanical properties and low melting temperature of the Sn-Zn solder is undeniable, however, the limitations regarding corrosion resistance present opportunities in furthering research in this field to identify improvements. This is to ensure that the corrosion performance can be aligned with the outstanding mechanical properties. The review also identified and summarized the advantages, recent trends and important findings in this field.Originality/value: The unique challenges and future research directions regarding corrosion measurement in Sn-Zn solders were shown to highlight the rarely discussed risks and problems in the reliability of lead-free soldering. Many prior reviews have been undertaken of the Sn-Zn system, but limited studies have investigated the corrosive properties. Therefore, this review focuses on the corrosive characterizations of the Sn-Zn alloy system.

The corrosion properties of Sn-9Zn lead-free solder was studied through potentiodynamic polarization in different concentration of hydrochloric acid (0.5, 1.0, 1.5, 2.0 M). Two types of polarization profile were observed for Sn-9Zn solder at lower concentration acid (0.5 to 1.0 M) and one at higher concentration acids (1.5 to 2.0 M). The morphological analysis showed that two distinctive structures of lamellar-like groove and irregular shaped of the corrosion product compounds formed on the solder surface after being polarized at different concentrations. Phase and elemental analyses revealed the formation of mixed corrosion product such as SnO, SnO₂, ZnO, ZnO₂, and Zn(OH)₂ on the surface after polarization.

Potentiodynamic polarization was used to studied the corrosion properties of SAC305 solder in different solution of 1.0 M HCl and 3.5 wt.% NaCl using the same scanning rate of 1.0 mV/s. The polarization curves indicated that corrosion in NaCl was less severe than in HCl solution based on corrosion current and passivation behavior obtained. Morphology and phases obtained after corrosion using SEM and XRD were analyzed. Microstructure analysis shows the present of compact corrosion product with presence of larger flake for polarization in NaCl compared to HCl. Phases present in XRD analysis confirmed the present of SnO and SnO₂ corrosion product for sample from both solutions.

Corrosion properties of Sn-0.7Cu solder were investigated in 1 M HCl. The scanning rates used were 0.5, 1.0, 1.5 and 2.0 mVs^-1 to study the aggressiveness level of HCl electrolyte in various environment. The morphological, elemental and structural of the samples were compared before and after the corrosion. Scan rate 1.0 mVs^-1 was chosen as the most optimum scan rate during corrosion analysis. The morphological analysis observed two types of corrosion product which is compacted and loosely-compacted corrosion product after the samples was polarized in 1 M HCl.

The corrosion analysis of SAC305 lead free solder was investigated in Hydrochloric acid (HCl) solution. Potentiodynamic polarization was used to polarize the SAC305. The effect of polarization on the phase and microstructure were compared to as-prepared SAC305 solder. Potentiodynamic polarization introduces mixed corrosion products on the surface of SAC305 solder. The XRD analysis confirms that the mixed corrosion products emerged on the surface after polarization by formation of SnO and SnO2 of which confirmed that dissolution of Sn was dominant during polarization. Microstructure analysis reveal the presence of gap and porosities produced limits the protection offered by the passivation film.