Effects Of Impurities On The Properties Of Tin-plating Solution In Methanesulfonic Acid System

Tin has non-toxic,good ductility,weldability,corrosion resistance,sulfur resistance,and decorative type.It has been widely used in food packaging,auto parts and electronic devices,etc.Tinplate is coated with pure tin on both sides of low-carbon steel,which combines the strength and formability of steel with various advantages of tin,and has been widely used in the food packaging industry.In recent years,as environmental protection issues have become increasingly tense,tin plating solutions in the methanesulfonic acid system have developed rapidly.However,in the production practice,a series of impurities will enter the bath,and the accumulation of impurities in the bath will affect the quality of tinplate production.The influence of SO₄^2-impurity on the performance of tin-plating solution in the methanesulfonic acid system was studied from the aspects of coating quality,electrochemical behavior,and bath stability.Electrochemical tests,neutral salt spray experiments,SEM,XRD,were discussed.Microscope observation,UV absorbance test,Zeta potential test and other analytical methods to explore the impact of SO₄^2-,Fe²⁺,Pb²⁺and tin mud on the performance of methanesulfonic acid tin plating solution.The test results show that when 0 g/L⁶0 g/L SO₄^2-is added to the bath,the cathode-limited cathode current density gradually decreases with the increase of sulfate concentration;when 100 g/L of sulfate is present in the bath,tin ions are The nucleation method changed;XRD tests showed that the presence of sulfate in the bath caused the surface texture of the coating to change.When there is no sulfate in the bath,the coating obtained on the polished Hull cell test piece is only（200）A diffraction peak on the crystal surface.As the concentration of sulfate in the plating solution increases,the diffraction intensity of the peak gradually decreases.Salt spray experiments and electrochemical tests show that when the concentration of sulfate in the plating solution is 5 g/L.The corrosion resistance of the coating is the best.When the concentration of sulfate in the plating solution exceeds 10 g/L,the corrosion resistance of the coating gradually decreases as the concentration of sulfate in the plating solution increases;when the SO₄^2-concentration in the plating solution is high at 60 g/L,the cloud point of the additive in the bath will be reduced;the sulfate radical in the bath will accelerate the production of tin mud.When the sulfate ion is present in the bath,the rate of decline of the solution will be faster than that without sulfuric acid.The rate of decline at the root is fast,indicating that sulfate is present Accelerate the production of tin mud.The test results show that the addition of Fe²⁺will increase the cathodic polarization of Sn²⁺deposition at lower overpotentials;the neutral salt spray experiment results show that the corrosion resistance of the coating when the concentration of Fe²⁺in the bath exceeds 10 g/L.The performance was significantly reduced;Neutral salt spray experiments and electrochemical tests showed that when a certain concentration of Pb²⁺was added to the bath,the corrosion resistance of the coating was improved.The XRF test results show that Pb²⁺will enter the coating during the tin deposition process.When the concentration of Pb²⁺in the bath increases from 0.02g/L to 0.5g/L,the content of Pb²⁺in the coating is correspondingly 0.04%.The increase is 0.3%.Neutral salt spray tests and electrochemical tests show that when tin deposits are present in the bath,the corrosion resistance of the deposits will decrease.