The 28-year old Colombian is set to spend six months with the Dons, who are without number one Jamie Langfield until October, and Brown is excited about his impending arrival.
"The deal was 90 per cent on the way last night," he told SunSport.
"And I'm delighted to hear that David is extremely keen to come to Aberdeen.
"We've been able to use the contacts that me and Archie Knox have at Manchester City to get him. Everything I've been told about the lad is excellent.
"City have good goalkeeping provision and that's made it difficult for David there.
"But he has great attributes, like his presence, his shot-stopping and dealing with cross-balls.
"City were happy for me to take him for a year. But out of respect for Jamie we're only signing David until the next transfer window in January.
"I have every intention of restoring Jamie to the team once he's fit again.
"David, I'm sure, will prove a real asset for us - but ultimately it will only be fair if we use our own goalkeeper.
"David, though, can use this as a great opportunity for him.
"If David has a successful spell with us then he can go back to Man City with his situation bolstered - or find that it's been a good shop window."