So Catholic Theology view Christians outside the the catholic church as the “invisible church”
It is Protestants who teach the existence of an invisible church. The Catholic Church does not.
adding on with the possibility of salvation.
As someone else mentioned, they are considered:
838 "The Church knows that she is joined in many ways to the baptized who are honored by the name of Christian, but do not profess the Catholic faith in its entirety or have not preserved unity or communion under the successor of Peter."322
Those "who believe in Christ and have been properly baptized are put in a certain, although imperfect, communion with the Catholic Church."323 With the Orthodox Churches, this communion is so profound "that it lacks little to attain the fullness that would permit a common celebration of the Lord’s Eucharist."324
Perhaps you mean to say that they are united in an invisible manner to the visible Church. In either case, I don’t think the rest of us are accustomed to the manner in which you are using the term, “invisible church”.
How do the orthodox view salvation outside the church. Is it the same as Catholicism?
There are many Orthodox churches. But this one says:
Because of the exclusive claims of the Lord, the Orthodox Church confesses, believes, and proclaims that the only Savior of the world, Jesus Christ, has one Body, His Church. We Orthodox believe in One Holy Catholic and Apostolic Church, and we believe that the Orthodox Church is it. In pluralistic societies such as those of North America and Western Europe today, the claim of the Orthodox Church to be the one and only Church that Jesus founded certainly is not popular, but ultimately it is a necessary outgrowth of the exclusive claims of Jesus; it is simply a testimony to the fact that God (Father, Son, and Holy Spirit) is One and that salvation is bestowed only by and through Him.
http://antiochian.org/content/what-about-non-orthodox-exclusive-claims-church
PS: Many Protestant’s I’ve spoken to believe Catholics go to hell
Yes. I’ve spoken to many who tell me so. The way I see it, they are making an honest mistake because of their religious fervor. Much like Saul. Therefore, I forgive them and pray that they will be converted like St. Paul.