Dear Arpan

A 5% solution of perchloric acid in glacial acetic acid gives good results as an electrolytic polish. The voltage for electropolishing is from 20 to 70 V and must be selected experimentally. Polishing time can be from 30 seconds to 5 minutes and depends on the quality of surface preparation before electropolishing (I usually prepare by sanding on sanding paper grit 800-1000 grid). If you lower the voltage to 1.5-5 volts, then electrolytic etching will occur (the etching voltage must also be selected experimentally for the best result). The electrolyte is prepared by adding perchloric acid to glacial acetic acid. Watch the temperature of the solution! - It should not exceed 30 degrees Celsius both when preparing the electrolyte and when working on it - flammable! This electrolyte is quite versatile and can be used for many steels.

For etching, you can also use a 10% aqueous solution of oxalic acid at a voltage of about 15 volts and a duration of 40-60 seconds.

For chemical etching, I can recommend the following reagents:

1) 100 ml of water, 300 ml of hydrochloric acid, 10 ml of nitric acid. If you let the reagent stand before etching for at least 2 hours, then the result will be better in my opinion.

2) Beraha II color etching:

The main solution is 800 ml of distilled water (it is advisable to use distilled water, not desalted water), 400 ml of hydrochloric acid, 48 g of ammonium hydrofluoride.

Before etching, add 1-2 g of potassium metabisulphite to the stock solution. The reagent is not stored for a long time, therefore, it is necessary to prepare it (add potassium metabisulfite to the main solution) immediately before etching. The best results are obtained in the first 2 hours of applying the solution. The etching time is selected experimentally.

304H Stainless Steel, I am generally use 10% aqueous solution of oxalic acid at a voltage of about 6 volts and a duration of 40-60 seconds. if not etching properly increase voltage up to 12 v and time to 120 seconds