Sete de Setembro was designed as an enlarged, and seaworthy, version of the casemate ironclad Barroso as part of the 1867 Naval Program, but she was ultimately classified as an armored frigate.

The hull was sheathed with Muntz metal to reduce biofouling and a bronze ram, 2.4 meters (7 ft 10 in) long, was fitted.

[2] Sete de Setembro had two John Penn & Sons 2-cylinder steam engines, each of which drove a single 3.7-meter (12 ft 2 in) propeller.

They were powered by four rectangular boilers that produced a total of 2,000 indicated horsepower (1,500 kW) which gave the ship a maximum speed of 12 knots (22 km/h; 14 mph).

[4] Sete de Setembro had a complete wrought iron waterline belt that was 3.04 meters (10.0 ft) high and had a maximum thickness of 114 millimeters (4 in).

Sete de Setembro was assigned to the Evolution Squadron in November 1885 despite having been reclassified in 1879 as a floating battery by virtue of her weak armor and lack of compartmentalization.