Being certified will certainly make you more marketable and will increase your negotiating power when it comes to discussing your salary. However as a non native English speaker I’m afraid you may still lose out to native English speakers with your same qualifications.

In other words, if you were on shortlist with a native English speaker who had very similar qualifications and background to yours then the post - and related high salary, would be more likely to be given to the native English speaker. However, if the native English speaker was under qualified or had no experience you would stand a very good chance of getting paid well despite not being a native English speaker.