This seems to be a recurrent issue in Google Chrome, although adding autocomplete off to the form did work in my build. Maybe in newer versions it doesn't anymore.
This is a hack. Give your input an id, say foo, and in JavaScript:
if (navigator.userAgent.toLowerCase().indexOf('chrome') >= 0) {
setTimeout(function () {
document.getElementById('foo').autocomplete = 'off';
}, 1);
}
Check if this works for you. The only downside to it would be that for those who use Chrome and have JavaScript disabled, the field would still be autocompleted.
