Effect of copper addition on the properties of electroless Ni-Cu-P coating on heat transfer surface

The effect of the copper content on properties of electroless Ni-Cu-P coating on heat exchanger surface was investigated, such as adhesion strength and surface characteristic, and anti-fouling property, which were considered to mitigate the accumulation of mineral fouling in the heat exchangers. The electroless ternary Ni-Cu-P coatings with different copper content were prepared on mild steel (1015) substrate surfaces by adjusting process parameters. Surface morphologies of coating and adhesion strength were investigated by using scanning electron microscopy (SEM) and MFT-4000 multifunctional material surface performance instrument, respectively. The results showed that the adhesion strength was improved with the addition of copper in the coating. With the increase of copper content, the deposition rate of ternary Ni-Cu-P coatings was increased, and the boundary of nodular became obvious. Moreover, the surface free energy of ternary Ni-Cu-P coatings was increased with the increase of copper content in the coatings and then decreased when enhancing the copper content further. The further fouling experiments indicated that all the ternary Ni-Cu-P coating surfaces with different copper content inhibited the adhesion of fouling compared with the stainless steel surface. The adhesion weight of fouling was approximately in proportion with the copper addition of ternary Ni-Cu-P coatings, but not the value of surface free energy. The work provides evidence that both adhesion strength and anti-fouling ability should be combined to use when applying surface modification in the field of heat exchanger.