We investigated the effects and interactions of the organic additives Polyquaternium-2 (PUB) and 1-benzyl pyridinium-3-carboxylate (BPC) in alkaline non-cyanide zinc electroplating. As PUB and BPC were added, the cathode potential of the polarization curve shifted in the negative direction at the same current density that occurred in the electrochemical experiment, and as confirmed by a scanning electron microscopy, the particles on the plating surface in the zinc deposits became finer, and the grain size decreased. Moreover, strong (101) and (002) peaks appeared in the X-ray diffraction pattern when no additive was added. However, as PUB and BPC were added, the intensity of the two peaks decreased, and an increase in the intensity of the (100) peak changed to a crystallographic orientation. With the addition of PUB and BPC, the gloss and whiteness gradually increased, and the surface roughness decreased. Finally, the throwing power tended to increase as PUB and BPC were added.

Zn–Ni alloy plating is widely applied in manufacturing of automobile and construction material components because it provides better corrosion resistance and wear resistance than Zn plating. Furthermore, chromate coating treatment is gaining attention with respect to improving the corrosion resistance of Zn–Ni alloys. In this study, we investigated the effects of NaF additive concentration and treatment time on trivalent chromate coating, which has been developed as an alternative to hexavalent chromate coating. The chromate post-treatment solution used in this study comprises Cr(NO3)3·9H2O (360 g/L), CoSO4·7H2O (40 g/L), and HNO3 (35 mL/L), to which NaF is added in the concentration range of 0–30 g/L. The as-formed coating films at 1.6 pH and 60 °C treatment temperature for deposition times ranging from 30 to 120 s demonstrated a decreasing corrosion rate as the NaF concentration increased. The electrochemical and morphological analyses inferred that NaF acted as a catalyst, enhancing the rate of film formation. Furthermore, the film thickness increased with the treatment time, and the film color changed in the order of yellow, purple, and green.

In this study, the effect of the hydrophilic–lipophilic balance (HLB) number and cloud point (CP) of a secondary-alcohol ethoxylated nonionic surfactant on degreasing efficiency was investigated. A degreasing process was conducted for steel samples with different surfactants in a degreasing solution. The HLB number and CP increased with the increasing n of the hydrophilic ethylene oxide (OCH2CH2)n group. For a constant temperature of the degreasing solution (30–80 °C), the degreasing efficiency was investigated as a function of degreasing time. The highest degreasing efficiency was observed near the cloud point of the surfactant, and the degreasing efficiency decreased significantly at temperatures lower and greater than the cloud point. A Hogaboom test was carried out to observe oil stains on the surface of samples. Additionally, the contact angle of the surface with water droplets was measured after degreasing with various surfactants.

Zinc (Zn) coatings, which are widely used to protect metals from corrosion, can be further improved by alloying with nickel (Ni). Increasing the Ni content enhances the corrosion-resistant properties of the Zn coating. This study investigated the effect of tetraethylenepentamine (TEPA) concentration on the Ni content and the properties of the Zn-Ni alloy coating. Zn-Ni alloy coatings were electrodeposited via the Hull cell test with TEPA concentrations of 0, 0.035, 0.07, and 0.1 M. We found that increasing the TEPA concentration improved the brightness of the coating at low current density and influenced the crystal orientation and morphology. When the TEPA concentration was increased to 0.7 M, the Ni content of the Zn-Ni alloy coating significantly increased before leveling off. However, the thickness of the coatings decreased with increasing TEPA concentration. The electrochemical behavior of the Zn-Ni alloy electrodeposition was validated via partial polarization curves of the Zn and Ni depositions.