Brush or vacuum dirt from the concrete. If there are oil stains, remove them with a concrete degreaser or alkali detergent. Rinse thoroughly with water.  If water beads up on the surface, the acid wash may not work correctly. Degreasing should solve this problem. Trisodium phosphate (TSP) cleaners are not recommended. Any residue left behind can react violently with the acid to release dangerous gas. Select a cleaning or etching product based on your experience level and project location:  Sulfamic acid is the safest to handle, and recommended for non-professionals. Phosphoric acid creates less fumes. Use it in rooms that contain stainless steel or other acid-vulnerable metals. It's also a good choice if you're just cleaning off mineral deposits. Muriatic acid (hydrochloric acid) is the most dangerous option and produces strong fumes. Recommended only for professionals working outdoors. These acids are some of the most dangerous substances available for home use. Wear acid-resistant gloves, rubber boots, and vapor proof goggles. Protect your lungs with a respirator with an acid-grade filter, and use fans to improve ventilation if necessary. Protect exposed skin with well-fitting clothing at minimum, and ideally with a face shield plus a PVC or Butyl coverall or apron.  Keep water nearby to wash spills from skin or clothing. Showers and an eye wash station are ideal. Keep baking soda or garden lime nearby to neutralize spills on the ground. Unlike metal, all common plastics are resistant to acid damage at these concentrations. To avoid a violent reaction, pour water in the bucket first, then add acid slowly. Defer to the manufacturer’s directions on the acid container over the guidelines below. These general ratios are suited to some mixes but not all:  Sulfamic acid: 1 pound powder or crystals per 1 gallon hot water (120 grams per 1 L water).  Phosphoric acid: dilute to 20–40%.  Muriatic acid: mix 3 to 4 parts water with 1 part acid, or follow label instructions for a 10% concentration (15% for hard, smooth...

TL;DR in Vietnamese:
Loại bỏ đất bẩn và dầu mỡ. Chọn axit. Tuân thủ các hướng dẫn an toàn. Rót axit vào nước đựng trong xô nhựa hoặc thùng nhựa.