International Aluminum Corp. of Monterey Park said Wednesday that it has agreed to be acquired by private equity firm Genstar Capital LLC for about $228 million.

The San Francisco-based equity firm offered to buy the 50-year old aluminum company for $53 per share in cash, a 6-percent premium on the stock’s closing price of $49.99 Tuesday.

International Aluminum said its board has approved the deal. Stockholders also must approve the transaction, which is expected to be completed in the second quarter. International Aluminum did about $280 million in sales last year.

Shares in the company were up $2.07 to $52.07 in midday trading.