Preparation And Properties Of Electroless Plating Coating On Anchor Rod In Support Engineering

The underground support engineering is a concealed work. As vital supportmaterial, anchors play an important role in the construction and safety aspects.Anchors are generally applied in the laneway, mine, tunneling and rock slopeengineering, in which they are prone to deteriorate under complex and adversegeological conditions, thus durability and service life of the anchor has been agreat threat. Wear and corrosion resistance of anchors has become the focus ofresearch.In order to predict the mechanical behavior of anchor rod passing throughthe complicated areas under harsh environments and increasing the usage ofanchor rod in bracing project, electroless plating was conducted to form Ni-Pcoating on RB400steel for improving the surface performance. The surface andcross-section morphology of the coating were measured by scanning electronmicroscope (SEM) and metallographic microscope, phase composition and sectional element distribution were determined by X-ray diffraction (XRD) andglow discharge optical emission spectrometry (GDOES). A reciprocatory typetribometer and electrochemical workstation were applied to evaluate the wearand corrosion resistance of anchor rod steel and Ni-P coating, respectively.On the basis of dual Ni-P plating, through a combination of chemicalplating after the heat treatment process, this article systematically studied theinfluence of heat treatment temperature on the morphology, structure and thecorrosion and wear resistance of Ni-P coating. With the increase of heattreatment temperature, surface transfers from amorphous to crystalline,crystallization degree increase, enhanced the cohesive strength between coatingand substrate, the coating surface hardness increases, the hard particle phaseNi3P plays dispersion strengthening effect to the coating. The analysis of frictioncoefficient, wear morphology and quality loss show that the coatings with theheat treatment temperature of400℃and450℃show excellent wear resistance.From the minimum corrosion current density, the coating at400℃behavesgood corrosion resistance.To explore the relationship between heat treatment temperature and thecorrosion resistance of coating, under the guidance of fractal theory, the authorchose the calculation method of fractal dimension, attempted to achieve a certaintheoretical basis in the analysis and judgment for the relationship. Fractal studiesshow that Ni-P alloy coating surface has fractal characteristics, fractal dimensionchanged with the coating corrosion resistance of a certain positive correlation. Because the fractal dimension represents coating surface morphology structureand the complex degree of visual, through the analysis of changed fractaldimension, it has certain feasibility to make some qualitative judgment aboutcorrosion resistant properties of coating.By adding rare earth lanthanum in the plating solution, comprehensiveanalysis was made concerning the La concentration influence on the structure,morphology, composition and wear and corrosion resistance of Ni-P coating.Rare earth lanthanum has remarkable effect on the Ni-P coating surfacemorphology in grain refining and modification. The coating structure hasobvious crystallite diffraction characteristics. The coating with the addingamount of0.25g/L is better, revealed mild wear degree in reciprocating weartest and presented a good wear resistance performance on the whole. Overall,the impact of rare earth addition on coating wear-resistance is inconspicuous.Electrochemical polarization curve and impedance analysis results show thatwhen the La3+content was0.50g/L, the coating has outstanding corrosionresistant performance, with the highest corrosion potential, the smallestcorrosion current density and the largest resistance between solution and matrix.