That's just your biased interpretation of Romans 6:3-18 in order to promote salvation by water baptism. You continue to confuse the picture (water baptism) with the reality (Spirit baptism). Now in regards to Romans 6:16, works-salvationists typically ignore "servants of obedience unto righteousness" and simply stress "obedience unto righteousness" as if works of obedience which "follow saving faith in Christ" are "unto righteousness," as if we are saved by works. Unbelievers are not slaves of obedience unto righteousness no matter how much so called obedience that they attempt to conjure up through the flesh in a vain effort to obtain salvation by works.
There is a contrast here between servants/slaves. There are only two kinds of servants/slaves in this world, in the spiritual sense; servants/slaves of sin unto death, or servants/slaves of obedience unto righteousness. When we place our faith exclusively in Jesus Christ for salvation/believe the gospel by trusting in His finished work of redemption as the ALL-sufficient means of our salvation, we then become "servants of obedience unto righteousness."
Before they obeyed that form of doctrine by choosing to believe the gospel (Romans 1:16), they had been slaves to sin. Romans 10:16 - But they have not all obeyed the gospel. For Isaiah says, "Lord, who has believed our report?"1 Peter 1:22 notice - "Purified your souls in obeying the truth" and notice in Acts 15:9 - "Purified their hearts by FAITH." "Obeying the gospel" and "obeying that form of doctrine" in these passages is really a synonym for believing the gospel. Being slaves of sin is put in the past tense. Paul goes on in Romans 6:18 - "You have been set free from sin and have become slaves to righteousness."
Notice in Romans 10:10 - For with the heart one believes unto righteousness..
Notice in Romans 4:5 - But to him who does not work but believes on Him who justifies the ungodly, his faith (not his works) is accounted for righteousness.
1Pe 1:22 Seeing ye have purified your souls in obeying the truth.. Being born again,