Lead print I

Lead print I

Material Name: Steel
Recipe No.: 12064
Primary Chemical Element in Material: Fe
Sample Type: Bulk
Uses: Lead segregation
Etchant Name: Lead print I
Type (Macro/Micro): Macro
Etching Method: Electrolytic
Etchant (Electrolyte) Composition: Bardgett and Lismer developed an electrolytic etching technique that reveals lead segregation. The disc is cleaned and electrolytically etched in a solution of ammonium acetate. Which can be prepared using either of the following procedures:
Method A: 50 g ammonium acetate, 1000 mL water
Method B: 75 mL glacial acetic acid, 900 mL water. Addition of ammonium hydroxide until the solution is just alkaline.
Procedure (Condition): The solution is placed in a stainless steel container which is attached to the positive terminal of a 6-V battery. The billet disc is placed on the bottom of the vessel, surface upward. A platinum wire loop extending across the surface is attached to the negative terminal of the battery and is suspended about 1/4 in above the sample surface in the solution. The loop is moved around above the surface for 30 to 60 s. The location of lead segregates are shown by the formation of a sharp brown stain.
Note: Lead, which is added to steels to improve machinability, requires special attention by the steelmaker in order to obtain a uniform distribution of the lead. Because of the potential variability in the distribution of lead, macroscopic testing is a key tool in quality control. Three techniques are available for revealing the lead distribution—macroetching, lead printing, and lead exudation. The latter tech- nique, frequently referred to as the lead “sweat” test, is the most frequently used because of its simplicity.
Reference: George F. Vander Voort, Metallography, Principles and Practice, ASM International, 1999, pp. 52-56.