With this global and U. S. crisis because of the coronavirus what is the possibility of the catastrophic devaluation of the dollar so that my buying power is greatly reduced?
1) The coronavirus is everywhere. It is not obvious it would affect the U.S. dollar differently than the Euro or Yen or Yuan. All the governments and economies are stressed, and so relative values will be unaffected.
2) Governments may respond to the economic stress differently. The U.S. will experience a flood of new currency as the Fed buys back government and bank securities and the Congress adds 2 trillion in deficit spending. That is inflationary, but in the face of massive downward pressure on prices due to the drop in consumer purchases and firm shutdowns, the net effect is likely to be small in the near term. The Fed will ease back as inflationary pressures appear and the economy recovers-- and so we are unlikely to see an out-of-control inflationary pressure.
For both of these reasons, I would not be overly concerned about inflation for the next 6 months. For added protection, you can purchase indexed government bonds that are pegged to the Consumer Price Index -- and that would protect you from a rapid devaluation of the dollar -- but I would use that just to protect the value of your holdings .