Immediate corrective action is really a misnomer. It is really a description of what was done after the problem or event was discovered. What actions were taken to contain the problem and stop it from continuing? If you were making bad parts, what did you do to stop making bad parts and what did you do about the bad parts you made? Immediate Corrective Action is where you describe the extent of the problem and the action taken to assure no other hardware is affected and that all affected hardware is identified.

For example, if there is a fire, the immediate corrective action would be to put it out. After it was out, you would determine how much damage was done. The damaged hardware and any hardware that is suspected to be damaged would need to be separated from the good and notify customers as appropriate. It is important to document any measures that are taken.

If it is possible that some of the impacted hardware may have escaped, guidance is available here.