Can an Armorer Artificer use Enhanced Defense or other Artificer Infusions on the armor or parts of the armor?

Question

Regarding Armorer artificer's Armor Model feature as describe in Tasha's Cauldron of Everything:

Your metallurgical pursuits have led to you making armor a conduit for your magic. As an action, you can turn a suit of armor you are wearing into Arcane Armor, provided you have smith's tools in hand.

Enhanced Defense

Item: A suit of armor or a shield. A creature gains a +1 bonus to Armor Class while wearing (armor) or wielding (shield) the infused item. The bonus increases to +2 when you reach 10th level in this class.

Can an Armorer use Enhanced Defense on the armor, since this is Arcane Armor?

I want to make sure since the feature does not say that a suit of armor that becomes Arcane Armor also turns into a magical suit of armor.

So I can assume it is not a magical suit of armor and can be infused, since the wording does not give the attribute "magical item" to an Arcane armor.

If indeed an arcane armor has magical effects, but without it being magical per se, then that leads to the extension of my question:

Because an armor "also expands to cover your entire body, although you can retract or deploy the helmet as a bonus action."

that means that it composes from different parts or it becomes a single piece suit, with pieces interconnected with each other? On which of those two cases can I add multiple infusions?

Answer 1

From 9th level, each component of the armor can be infused, and by extension, the armor should be infusable with one infusion at earlier levels.

The Armorer's 9th level feature Armor Modifications reads:

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.

So from 9th level onward, the four components of your Arcane Armor can be given a different infusion. To me, it seems that "armor now counts as separate items for the purposes of your Infuse Items feature" indicates the prior to 9th level, it counted as a singular item for the purposes of your infuse items feature.

At earlier levels, the question is "does the armor count as a "nonmagical object" as required by the Infusions feature:

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

Reading through the subclass description, the armor itself is never explicitly stated to be magical, but there is a sentence in the beginning of the subclass description that to me says "yes, you can infuse the armor":

The artificer bonds with this armor, becoming one with it even as they experiment with it and refine its magical capabilities.

It seems to me that the only thing this experimentation with the armor could be referring to would be adding various infusions to it. The only other change the artificer could make to the armor is swapping out for the other of the two models, which does not seem to fit "refine its magical capabilities". So based on the description, it seems clear enough that the intent is that the Arcane Armor be eligible for one infusion prior to 9th level.

All that said, I must provide the caveat that there is some room for a DM to rule that the Arcane Armor is not eligible for infusions prior to 9th level, though I would certainly allow it.