ASTM B343-92a(R2020) pdf free download

ASTM B343-92a(R2020) pdf free download.Standard Practice for Preparation of Nickel for Electroplating with Nickel
1. Scope
1.1 This practice summarizes well-known, generally practi- cal methods for producing adherent electrodeposits of nickel on nickel. 1.2 Electrodeposits of nickel on nickel are produced, for example, to improve the performance ofdecorative coatings, to reclaim electroplated parts that are defective, and to resume nickel electroplating after interruptions in processing. Interrup- tions may be deliberate, for example, to machine the electrode- posit at an intermediate stage in the electrodeposition of thick nickel coatings. The interruptions may be unintentional, for example, resulting from equipment and power failures. 1.3 To ensure good adhesion ofnickel to nickel, precautions should be taken to avoid biopolar effects during nickel elec- troplating. This is of particular importance in return-type automatic plating machines where one rack follows another rack closely. Bipolar effects can be avoided by making the racks cathodic while they are entering or leaving the nickel tank. Separate current control on entry and exit stations is desirable. 1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.6 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Cleaning
3.1 The following cleaning treatments may be used for all conditions and types of electrodeposited nickel. The choice of the procedure will be governed largely by the condition of the surface. 3.1.1 Degreasing—Degreasing is used to remove the bulk of grease, oil, and buffing compounds that may be present on the surface. The cleaning may be effected with vapor degreasing, organic solvents, emulsion cleaners, or soak cleaner. 3.1.2 Electrolytic Alkaline Cleaning—Removal of final traces of dirt, grease, and oil is accomplished best with electrolytic alkaline cleaning. The solution may be either a proprietary cleaner or a formulated one. Since a nickel surface forms an oxide coating if treated anodically in an alkaline solution, this condition must be altered in subsequent steps if it cannot be avoided.
4. Activating
4.1 The procedure used for etching or activating the nickel surface usually determines the soundness of the adhesion. The choice of the procedure may be governed by the condition of the surface and possibly the type of nickel. The milder etching treatment should be used in the case of highly finished surfaces, but it may result in sacrificing maximum adhesion.The thickness of the nickel may militate against the use of certain etching procedures, and therefore the thickness re- moved is indicated for each procedure described in 4.2 to 4.8. 4.2 Anodic Treatment in Concentrated Sulfuric Acid— (Nickel removed nil). A70 mass % sulfuric acid solution containing 661 mL of concentrated, 96 mass % sulfuric acid (density 1.83 mL) diluted to 1 L may be used for activating the nickel surface provided the temperature of the solution is not over 30 °C (see Warning). When the initial mixture cools, dilute to exact volume. The time of treatment should be about 1 min at a current density of 10 A/dm 2 . At this current density the nickel normally goes passive and a bright surface becomes only slightly dull. This type of passivity is removed by subsequent rinsing in water. (Warning—Slowly add the sul- furic acid with rapid stirring to the approximate amount of water required.) 4.3 Anodic Etching in Sulfuric Acid—(Nickel removed approximately 1.3 µm.) A25 mass % sulfuric acid solution, containing 166 mL of concentrated, 96 mass % sulfuric acid (density 1.83 g/mL), diluted to 1 L is used for this anodic etching treatment in which the nickel surface is first etched at a low current density of 2 A/dm 2 for 10 min and then made passive at 20 A/dm 2 for 2 min and finally cathodic for 2 or 3 s at 20 A/dm 2 . See Warning in 4.2. The temperature of the solution should be kept below 25 °C. This treatment results in excellent adhesion, but the amount of etching makes it less desirable for a highly finished surface.