ELECTROLESS COMPOSITE COATINGS OF Ni-P-NANO-TiO2 (ANATASE-TYPE) AND ITS CORROSION RESISTANCE

Effects of process on the deposition rate,corrosion resistance and pitting corrosion potential of Ni-P-nano-TiO2 (anatase-type) electroless composite plating were studied by using weightloss corrosion method,magnetic thickness gauge and electrochemical methods.The results indicated that the optimum formula and process were composed of NiSO4(10 g/400 ml),NaH2PO2(10 g/400 ml),NaAc(6 g/400 ml),H3BO3(6 g/400 ml),1 h,pH 5.0,80 ℃,100 r/min and nano-TiO2 particles (anatase) 3 g/400 ml.In salt corrosion media,corrosion resistance of Ni-P-nano-TiO2 (anatase) electroless composite coatings increased by 8 times,compared with that of electroless coatings of Ni-P.However,in basic and acid corrosion media,its corrosion resistance didn’t increase.