Be the change you wish to see in the world.
—Ghandi (bumper stickerized)
These sorts of things tend to be much better received when introduced voluntarily, so volunteer. Put up a gerrit server or similar and start putting your own changes on it. Tell a few people you're trying to improve your code quality and ask if they wouldn't mind reviewing your code. When people ask you to informally review their code, request they put it on gerrit. Make it open for anyone to use.
At the very least, your own code quality will improve. You will find out who really cares about code quality and who is resistant. You will see how your colleagues prefer to use it, and can use that to create guidelines if it's later made mandatory. Company-wide, it might continue indefinitely as volunteer only, or if you already have a disciplined team that does informal reviews you might find out it's not worth the trouble.
What often happens is a release will have a lot of quality problems, management will start freaking out about how to prevent that in the future, and will look around for solutions. If you have this volunteer process in place that is already working well for some, it's likely to be given management support company-wide at that point. At my company, our agile process, automated testing, and modularization efforts all basically started as volunteer ideas.