In a certain chemical blanking operation, a sulfuric acid etchant is used to rem
ID: 1050275 • Letter: I
Question
In a certain chemical blanking operation, a sulfuric acid etchant is used to remove material from a sheet of magnesium alloy. The sheet is 0.25 mm thick. The screen resist method of masking permits high production rates to be achieved. As it turns out, the process is producing a large proportion of scrap. Specified tolerances of plusorminus0.025 mm are not being achieved. The foreman in the CHM department complains that there must be something wrong with sulfuric acid. "Perhaps the concentration is incorrect, " he suggests. Analyze the problem and recommend a solution. (in order to understand the details of the process, you may need search more information on the web about the process characteristics and factors that affect accuracy, such as different methods of masking and process parameters control).Explanation / Answer
Ans:-
To achieve specified tolerance of +/- 0.025 mm, concentration of etchant (Sulphuric acid) should be very selective because as Sulphuric acid is very reactive and resulting in large proportion of scrape.
Sulphuric acid may be replaced by Phosphoric acid solution to get better results.
For corrosion inhibition in micro defects of protective coatings on magnesium alloy scanning vibrating electrode technique or scanning ion-selective electrode technique in 0.05 M NaCl may be employed.