Alcoa (AA) pushed to aggressively roll up aerospace component suppliers earlier in the decade on the belief that the markets weren't interested in a raw material producer tied to the commodity cycle. But on Tuesday, the first day the two parts of Alcoa traded as independents, it was the finished goods unit that received a cold welcome on Wall Street.

On Tuesday afternoon, the new Alcoa, a spinoff that contains the aluminum mining and production operation, traded up more than 7% while Arconic  (ARNC) , the maker of finished parts for the automotive and aerospace industries, traded down by a similar amount.

The split, announced in September 2015, like the initial rollup was the product of CEO Klaus Kleinfeld's plan to revitalize the 128-year-old company and make it better able to compete against a surge in supply that has come online in emerging markets. In recent years Alcoa did a series of high-profile deals including buying Firth Rixson for $2.85 billion and RTI International Metals for $1.5 billion to build the downstream operations that now trade as Arconic.

The new company has annual sales of about $12.5 billion, with about 65% derived from markets that Alcoa described as "characterized by secular growth and compelling margins." The red-hot aerospace market accounts for about 40% of Arconic revenue, selling metal-based products that go into airframe structures and engines.

But Alcoa's last quarter as a combined entity, in which it missed analysts' expectations by 2 cents a share on sales that fell about $130 million below consensus, are likely giving would-be investors in Arconic pause on its first day of trading. The company said earlier this month that full-year downstream revenue would come in below previous forecast.

Kleinfeld told investors on an Oct. 11 call that the Arconic businesses were hit by customer-specific issues, including some development delays related to new aircraft engines, but insisted the shortfalls were temporary setbacks and not a sign of weakness. The CEO, who is staying with Arconic, continues to believe that what he calls the "aluminization" of the auto business as manufacturers increasingly turn to the lightweight metal to meet stricter fuel economy guidelines.

Arconic is going to need that growth, as the split was designed in such a way to shed Alcoa's debt at the expense of the downstream operations. Alcoa, which has spent recent years streamlining its refining operation and closing higher-cost facilities, handed Arconic all of the combined company's $9 billion in total debt and $3 billion of the combined $5.6 billion in estimated pension obligations.

In theory, Arconic and its higher margin, faster growing operations should be able to more easily service the borrowings, while Alcoa needs the flexibility of a pristine balance sheet to adjust to changes in the commodity cycle and to fight off lower-cost foreign competition. Investors on Tuesday seemed unwilling to bet that the growth Kleinfeld sees on the horizon will materialize as quickly as the CEO hopes.

Arconic will have some help coming its way soon, as post-split Alcoa intends to raise about $1 billion as a standalone with proceeds used to pay down the debt of the downstream business. Arconic also holds a 19.9% retained interest in Alcoa available for monetization if it needs debt relief, or if Alcoa shares continue to surge.

Jim Cramer's Action Alerts PLUS Charitable Trust Portfolio owned 2,700 shares of Alcoa prior to the separation; it now owns 2,700 shares of Arconic and 900 shares of new Alcoa.

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