The trouble is, by using the Bible alone you can make a case for believing that redemption and salvation are the same things, especially for those Protestants who like to string verses together without regard to their context and read into them what they want them to say.
However, do not despair. It is not that hard to explain. Redemption is what Jesus did for all of us on the cross. They will certainly agree with that. When we take advantage of that redemption we can be saved, which not everyone does, and they will agree with that too. Our redemption was involuntary but taking God up on it, the being saved part, is up to us to do.
When I was in the Assemblies of God there was a big argument raging amongst us about this issue and I don’t expect it’s changed since then, so don’t expect all Protestants on the Evangelical side of Christianity to agree.