Electrochemical Analysis of Electroless Nickel Plating Rate

Electroless Ni-P alloy plating has excellent corrosion resistance, wear resistance, magnetic shielding, weldability, etc., and is suitable for plating of various materials and complex shapes. As a new type of surface engineering material, electroless plating NP alloy has been widely used in petroleum, chemical, electronics, printing, automotive, aerospace, food and other industrial enterprises. However, due to the high operating temperature, the following problems usually occur in popularization and application: high energy consumption, adverse labor conditions, and serious equipment wear and tear.

Affected by environmental factors, such as foreign impurities, other ions into the bath, nickel ions will be the center of their catalytic reduction, resulting in its own chain reaction and decomposition, resulting in sediment or plated in the plating tank thick The alloy layer causes a vicious cycle of the plating solution to be wasted, the utilization of the medicine is greatly reduced, and the cost is also increased.

If the plating on the plastic substrate, it will cause deformation of the plastic under high temperature, affecting the bonding performance between the coating and the substrate and the special requirements of the plastic shape in the actual work process.

In order to obtain an excellent coating, some process conditions (such as pH, reducing agent type, and concentration) cannot be changed. When the other conditions are not changed, if the plating temperature is lowered, the ion activity will decrease, the diffusion rate will slow down, and the oxidation-reduction potential will decrease, which will eventually lead to a difficult deposition reaction. For this reason, it is necessary to study various types and concentrations of additives in order to increase the chemical deposition rate at low temperatures.

In the past, the deposition rate of electroless nickel plating was commonly used for weight gain and thickness measurement. Electrochemical analysis was used to study the deposition rate of electroless nickel plating. According to the theory of mixed potential of electroless nickel plating: When electroless plating is carried out, Ni2 is reduced by H2PO2 to deposit Ni. The process is composed of oxidation of anode reaction hypophosphorous reducing agent and cathode reaction Ni2+ reduction to Ni two independent parts: 4 Therefore, it is necessary for us to separately discuss the effects of additives on the two processes of cathodic reduction of metal ions and anodizing of reducing agents. That is, by measuring the absence of Ni2+ and H2PO2 in the electroless nickel plating solution, the other components are not changed. The polarization curve of the system was used to study the effect of additives on the actual electroless nickel plating process. The method we used was to determine the deposition rate of electroless nickel plating by controlling the polarization curve of each reaction during electroless nickel plating after adding different additives to achieve the purpose of controlling the entire process. The advantage of this method compared to the conventional method of measuring the deposition rate by the weight gain method is that the effect of the additive on the deposition rate of electroless nickel plating can be judged without actual plating, and thus the actual reduction can be seen. Additives that reduce the ability to activate the reaction also increase the rate of deposition. Additives (S+Y) increase the degree of anodic oxidation to a greater degree than anodic oxidation (Sodium acetate + S).

2.3 Weight gain method Accurately weigh the sample and place it in the plating bath for 1 hour and take it out.

(1) In experiment 1, 5 plating solutions of sodium acetate, succinic acid, lactic acid, and triethanolamine were added to the basic plating solution and the basic plating solution respectively; under the condition of 1 h, the precipitation additive was sodium acetate+S plating. The addition of additives to the XRD pattern of the S+Y coating reduces the deposition rate by adding XRD patterns. When lactic acid is used as a complexing agent, the addition of additives can increase the deposition rate of the electroless plating. Among them, S+Y has the most obvious effect on the deposition rate. . Therefore, the deposition rate of electroless nickel plating can be controlled by adding different additives.

(3) The results obtained by electrochemical analysis using the gravimetric method indicate that the method of electrochemical analysis for the deposition rate of electroless plating is feasible.

Through the electrochemical analysis of screening additives, an actual amorphous nickel-phosphorus alloy can be obtained by actual plating.