ASTM B507-86 pdf free.Standard Practice for Design of Articles to Be Electroplated on Racks.
This practice covers design information for parts to beelectroplated on racks. The recommendations contained hereinare not mandatory, but are intended to give guidance towardgood practice.This standard does not purport to address all of thesafety concerns，if any,associated with its use. lt is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.
When an article is to be electroplated, it is necessary toconsider not only the characteristics of the electroplatingprocess， but also the design of the part to minimize electroplating and finishing costs and solution dragout as well as toimprove appearance and functionality. It is often possibleduring the design and engineering stages to make smalladjustments in shape that will result in considerable benefittoward a better quality part at a lower cost.
The specific property of an electroplating process thatwould require some attention to the details of optional designs,is the throwing power of the electroplating solution. Throwingpower is the improvement of the coating distribution over theprimary current distribution on an electrode (usually cathode)in a given solution, under specified conditions.The apparent current during practical electroplating isnever uniform over the surface of the product. Even parallelplates have a nonuniform distribution of current when freelysuspended in a bath as shown in Fig. 1. In this example, thecurrent lines tend to concentrate as corners, and edges (highcurrent density) of the part. Consequently more metal isdeposited at the highcurrent density areas than at the low-current density areas.Throwing power is not the same for all metals and allelectroplating baths.Table 1 lists the commonly used electro-plating processes. They are arranged according to decreasingthrowing power.A Rochelle-type copper electroplating solution has ex-cellent throwing power compared to the poor throwing powerof a chromic acid solution used to deposit chromium. Thewidely used Watts-type nickel bath has fair throwing power.5. Geometric Factors Determining Deposit Distribution5.1 Since a metal deposits preferentially at protuberances,such as sharp corners,edges, fins，and ribs, these should be rounded to a radius of at least 0.4 and preherabIcornoer in aavoid excessive buildup. Contouring a base corner in a depression is also recommended to avoid thickness deficiencyat the location.The width-to-depth ratio of a depression or recessshould be held to more than three as shown in Fig. 2.Otherwise, a special auxiliary anode must be employed insidethe recess to promote more uniform current distribution. An
auxiliary anode is usually made of the depositing metal amatasplaced close to the low-current density areas to enhance metal deposition at those regions.All sharp edges and base angles of a recess should berounded to a radius of 0.25 times or more the depth of therecess as shown in Fig. 3. When sharp recess angles arerequired for a functional purpose, the electroplater cannot beexpected to meet a minimum thickness at those locationsunless it is specifically required.ASTM B507 pdf download.