Rules for Artificer's Infusion (Lvl 2):

Whenever you finish a long rest, you can touch a nonmagical object and imbue it with one of your artificer infusions, turning it into a magic item.

Rules for Armorer's Arcane Armor (Lvl 3):

As an action, you can turn a suit of armor you are wearing into Arcane Armor, provided you have smith's tools in hand.

Rules for Armorer's Armor Modifications (Lvl 9): 

At 9th level, you learn how to use your artificer infusions to specially modify your Arcane Armor. That armor now counts as separate items for the purposes of your Infuse Items feature: armor (the chest piece), boots, helmet, and the armor's special weapon. Each of those items can bear one of your infusions, and the infusions transfer over if you change your armor's model with the Armor Model feature. In addition, the maximum number of items you can infuse at once increases by 2, but those extra items must be part of your Arcane Armor.

RAW, it seems I can make Mithral Armor into Arcane Armor (no magical status limitations). But RAW, can I apply Artificer Infusions on my Arcane Armor-ized Mithral Armor?