DOW 19, also known as chromic acid, is a treatment that is used on magnesium parts that need spot touch-up to repair minor damage. It can also be used as a temporary coating to prevent corrosion between production processes. This coating is extremely thin and offers no corrosion resistance. DOW 19 also contains hexavalent chromium (aka:Cr6+), which is known to be a very toxic chemical. This coating is applied at room temperature by either immersion in a tank or by brushing the solution onto the base magnesium. Because DOW 19 is allowed to react with the base magnesium for 1-3 minutes, the magnesium will turn into dark brown color.
The tables below illustrate how Dow 19 and Dow 7 stand in comparison to Tagnite in terms of corrosion resistance.