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The cathode efficiency depends on the process and varies between 90 and 97%. Due to this mismatch, during the plating the nickel concentration in the solution and the pH will slowly rise. [6] The process takes minutes to hours depending on the current density and the intended thickness of the plating. [7]
The main ingredients of an electroless nickel plating bath are source of nickel cations Ni 2+, usually nickel sulfate and a suitable reducing agent, such as hypophosphite H 2 PO − 2 or borohydride BH − 4. [1] With hypophosphite, the main reaction that produces the nickel plating yields orthophosphite H 2 PO − 3, elemental phosphorus ...
In electromagnetism, current density is the amount of charge per unit time that flows through a unit area of a chosen cross section. [1] The current density vector is defined as a vector whose magnitude is the electric current per cross-sectional area at a given point in space, its direction being that of the motion of the positive charges at this point.
It measures useable current density range, optimization of additive concentration, recognition of impurity effects, and indication of macro throwing power capability. [14] The Hull cell replicates the plating bath on a lab scale. It is filled with a sample of the plating solution and an appropriate anode which is connected to a rectifier. The ...
Regardless of the driving force, the current density is found to be greatest at the conductor's surface, with a reduced magnitude deeper in the conductor. That decline in current density is known as the skin effect and the skin depth is a measure of the depth at which the current density falls to 1/e of its value near the surface. Over 98% of ...
This ongoing current in both directions is called the exchange current density. When the potential is set more negative than the formal potential, the cathodic current is greater than the anodic current. Written as a reduction, cathodic current is positive. The net current density is the difference between the cathodic and anodic current density.
The upper graph shows the current density as function of the overpotential η . The anodic and cathodic current densities are shown as j a and j c, respectively for α=α a =α c =0.5 and j 0 =1mAcm −2 (close to values for platinum and palladium). The lower graph shows the logarithmic plot for different values of α (Tafel plot).
Black nickel plating was developed around 1905, and between the two wars, black chrome plating (first German patent 1929.GP 607, 420), which saw wider use only from the mid-1950s. [14] After the First World War, the first procedures for anodic oxidation and coloring of anodically oxidized aluminium were developed (1923, 1924.DRP. 413876).