Improving the Adhesion and Resistance to Erosion Corrosion of Electroless Nickel-Phosphorus Coating Applied on Ductile Cast Iron Using Nickel Intermediate Layer

Electroless nickel-phosphorus coatings are widely used in industries due to their excellent corrosion and wear resistance. These coatings are applied on various substrates, but the coating applied on parts made of cast iron does not have good adhesion due to the presence of graphite in their structure, and cast irons are usually not coated by this method. This research aims to provide a solution to improve the adhesion of electroless nickel-phosphorus coating to the ductile cast iron substrate with spherical graphite. For this purpose, the surface of GGG۵۰ cast iron was coated using an intermediate layer of nickel applied by electroplating, and the electroless coating was deposited on this intermediate layer. Different microscopic methods were used to examine the applied coating, and its adhesion was tested according to the ISO ۲۸۱۹ standard. Also, the corrosion resistance of the coating in different thicknesses was examined by Tafel polarization tests and electrochemical impedance spectroscopy, which revealed that the coating with a thickness of ۴۸ microns had a corrosion rate of ۰.۴ mpy which was the lowest corrosion rate and ۱۳ times more resistant than uncoated cast iron. Also, the erosion-corrosion test was performed using the slurry pot method for ۱۶ hours on this coating and the substrate. In this test, there was no separation of the coating, and the degradation rate of the coating was ۸.۱۵ mpy, which, compared to uncoated cast iron with a degradation rate of mpy ۳۸۱, had a ۴۶-fold improvement.

کلیدواژه ها:

Corrosion ، Electroless nickel – phosphorous ، Electrochemical impedance spectroscopy ، Erosion corrosion ، Ductile cast iron. ، خوردگی ، الکترولس نیکل – فسفر ، طیف سنجی امپدانس الکتروشیمیایی ، خوردگی فرسایشی ، چدن نشکن