Associated Press: The owner of the rig that exploded in the Gulf of Mexico has told federal investigators that the now infamous blowout preventer is in danger of corroding and its value as a key piece of evidence may be compromised. Transocean lawyer Steven Roberts said in a Nov. 3 letter to the federal investigation team that forensic testing had not yet begun on the device even though it’s been sitting at a NASA facility in New Orleans for two months. He said it may be corroding because of inadequate preservation….