Touch upâs should be done minimum 4-6 weeks post the initial treatment. This allows time for eyebrows to heal fully before perfecting them for the second time. Free touch-ups are only valid up to 3 months from initial procedure date.
Re: The Tinny sound? Most folks that are concerned about a tinny noise with aluminum boats are referring to the noise generated by the hull moving through the water (which can be modulated/reduced through many different avenues). You mention vibration and rpms, so I'm guessing that you're not referring to that sound.
  I can tell you if a magnet sticks to an item then it is steel or iron. I know this because i weld and i use a magnet to decide what i can weld and what i can't. Aluminum â¦ is not magnetic. You can tell aluminum by it's dull silver color or it can be highly polished.You can also tell by the weight. I know even less about bronze but i think it would be a heavy metal and often darker and brownish color. Brass will be a lighter weight and a higher shine and more of a goldish color. Copper well....it looks like the color of a penny. That's assuming it's not metal that's painted or something.