I had read some years ago an article describing the decision of an emperor to deal with the empire's economic troubles be devaluating the currency. The devaluation occured by mixing silver with not so precious metals. That policy was continued by the successor emperors but in the end the only thing they managed to achieve was to cause a tremendous inflation. I am trying to find out infos about this incident, the time span in which it happened and the emperor that initiated it. Any info or links to books about this policy will be most welcome
To summarise, the basic coin was the denarius, introduced in 211BC. Its size and the amount of silver in it gradually shrank over time; debasement of the coins was a fairly continuous process. The exact reasons for it aren't clear, but shortages of precious metals, and inadequate state finances probably had a lot to do with it. Debasement usually increased when the empire was weak.
I wanted to expand on my comment; the traditional formulation of the economic principle is "Inflation is a tax for which nobody has to vote." In an autocracy like the Roman Empire, the maxim would be slightly adjusted, "Debasement is a way of funding the government without generating opposition from strong stakeholders."
Debasement reduces the buying power of the individual and shifts that buying power to the state - it reduces the wealth of everyone who stores wealth in coin. Like most "flat" taxes, it is regressive and has a greater impact on the poor. Like most flat taxes, it is also easier for the wealthy and powerful to minimize the impact of the tax. (when debasement is imminent, shift wealth to non-coin assets such as land or art.)
Infographic summarizing Roman currency debasement - Note the graphic "Silver content of an individual denarius" - debasement occurred repeatedly and frequently. There was no single event.