Corrosion Resistance of Low Pressure-cold Sprayed Nickel-Zinc-Alumina Composite Coating in Natural Sea Water

Nickel based coating reinforced with alumina and zinc was prepared on Q235 steel using low pressure cold gas dynamic spray method. Surface morphology and cross section of the coating were studied by SEM and EDS. Corrosion protection properties of this coating were tested with nature sea water immersion method and EIS. No red rust was observed on the specimen after 60 days immersion, and the simulated coating resistance after 30 days immersion retained at a rather high level, which means the coating has good corrosion resistant properties and the coating can protect steel substrate from corrosion. There are two main reasons for good corrosion resistance of this coating. First, the dense corrosion product Zn(OH)2 produced by Zn corroding blocks penetrated cracks in the coating and thus reduces the permeation of seawater. Second, nickel can stabilize the produced Zn(OH)2 to extend its protecting time.