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Types of Etching

    Results from the polishing process will be a shiny mirror-like surface. So that the metal structure is clearly visible, the surface is be etched. Here are some of the etching solution for macro and micro examination commonly used in metallography.

A. The Macro Materials solvent etching;
a. Hidrochloric, composition 50% hidroclhoric acid in water by using a temperature of 700-800 up to one hour. Its use for iron and steel.

b. Sulphuric, composition is 20% sulfuric acid in water with a temperature of 80% using the time taken 10-20 seconds. Its use for iron and steel materials.

c. Nitric, composition 25% nitric acid in water, such as a and b may be cold if it fits. Its use for iron and steel materials.

B. The Micro Materials solvent etching
A. Nitric acid, nitric acid composition 2 ml, alcohol (95%) 98 ml. Use FOR CARBON steel, Low Alloy steel and steel alloys being. Time Up One Minute

b. Picric acid, picric acid composition 4 grams, 98 ml of alcohol. Use steel FOR CARBON hearts normal circumstances, softened, hardened and tempered. Etching time of a few seconds until one minute.

C. Stages Etching
Etching process steps in the inspection of metal structures are, as follows:
a. Prepare etching solution into the cup
b. Dip the surface of the specimen into the solution by using a small pliers clamp tool immersion few seconds to adjust to the needs
c. Clean the specimen with clean running water and then wipe with alcohol
d. The test specimen then dried with a clean cotton dry it with a dryer or a special (for example Hair Dryer).

D. Effect of Etching
Effect of reaction from a chemical solution to the surface of the test object is the entire surface will appear as irregular lines that indicate the emergence or existence of the boundaries between the crystal grains of the metal.