The Cameroon international has failed to impress at Upton Park since he joined The Hammers from Liverpool in a £2.5 million deal, and will now be shipped out to the German Bundesliga.
The 25-year-old will be looking to leave East London in a bid to get regular football ahead of Cameroon's involvement in the World Cup next summer.
He is also unhappy at the way he has been treated by Hammers boss Glenn Roeder, and is angry that he seems to have been blamed for all of West Ham's defensive flaws this season.
"The manager has to show me respect and at the moment he is showing me none," said the Cameroon skipper.
Cologne are struggling near the foot of the table and would like to bolster their squad, although West Ham insist the deal has not been sealed just yet.
"There is a possibility Rigobert will be going to Cologne in a loan deal but nothing has been finalised," said Hammers managing director Paul Aldridge.
