Short answer. No. A decree separating your property does not touch debts you already owed. The Code says separation of property shall not prejudice rights previously acquired by creditors, so a creditor whose claim existed before the decree can still reach what he could have reached before it.
What the law says
The separation of property shall not prejudice the rights previously acquired by creditors.
Family Code, Article 140 — Separation Does Not Prejudice Prior Creditors. Read the full provision →
One sentence, and it is a shield for creditors
Article 140 says the whole of it: the separation of property shall not prejudice the rights previously acquired by creditors. The provision exists because the alternative is obvious. If a couple could rearrange their property regime and thereby put assets beyond the reach of people they already owed, every separation of property would be a debt-avoidance device and no creditor could safely lend to a married person. So the decree operates going forward, on how the spouses hold property from that point, and leaves existing claims exactly where they stood.
Previously acquired is about the date of the right
The line is drawn at when the creditor's right arose, not at when he sues or discovers the decree. A loan taken during the marriage, an unpaid supplier, a judgment already rendered, taxes already due — all of these are rights previously acquired, and a decree obtained afterwards does not shrink them. What the decree does change is the future: obligations one spouse incurs after separation of property is decreed are that spouse's own, and the other spouse's property is not the natural fund for them. Nor does it matter that the creditor consented to the petition or said nothing about it; consent to the dissolution is not a waiver of the debt.
Which is why the petition has to name them
This is the reason a petition for voluntary dissolution must list all creditors of the community or partnership and the personal creditors of each spouse, and notify them of the filing, with the court taking measures to protect them. Article 140 states the substantive rule; the notification requirement is how it is enforced in practice. A creditor who was never told still keeps his rights — the omission does not extinguish anything — but it does put the honesty of the petition in issue, which is a poor position for the spouses to be in.
Draw the line by date before you file
Make a schedule of every obligation with the date it was contracted and the property that answers for it: mortgages and the assets they encumber, personal loans, credit lines, tax assessments, judgments. Debts on the wrong side of the decree do not disappear, so the useful exercise is working out which of them the community was liable for and which were always personal — that is what determines whose property pays, both before and after. Separation of property is a planning tool, not a way out of what is already owed. A lawyer will want that schedule before advising on whether to file at all.