The Acciaio-class submarine (also sometimes called Platino class[1]) was the fifth subclass of the 600 Series of coastal submarines built by the Regia Marina. They were completed during the early 1940s and saw service in World War II.
The Acciaios were a development of the and designs, with some improvements, such as a lower conning tower to improve stability and reduce the silhouette. Of the 13 vessels in the class, six were built by CRDA at Monfalcone, four by OTO at Muggiano, and three by Cantieri Tosi in Taranto, the three main Italian shipyards for submarines. They were single-hulled with side tanks, and built to a Bernardis design, though the Tosi vessels had more powerful engines (at the expense of the two stern torpedo tubes), giving a surface speed of .
The word Acciaio means "steel", and all vessels in this class were named for metals and minerals.
| Ship | Builder | Launched | Fate | ||
|---|---|---|---|---|---|
| OTO | 20 July 1941 | data-sort-value="13 July 1943" | torpedoed 13 July 1943 by | ||
| CRDA | 18 December 41 | data-sort-value="14 September 1942" | bombed 14 September 1942 by Allied aircraft | ||
| Tosi | 22 February 1942 | data-sort-value="3 August 1943" | sunk 3 August 1943 by | ||
| CRDA | 25 June 1941 | data-sort-value="17 February 1943" | sunk 17 February 1943 by,, | ||
| CRDA | 6 September 1941 | data-sort-value="8 February 1943" | sunk 8 February 1943 by | ||
| Tosi | 28 September 1941 | data-sort-value="12 July 1943" | captured 12 July 1943 by British destroyers | ||
| OTO | 20 July 1941 | data-sort-value="12 August 1942" | rammed 12 August 1942 by | ||
| CRDA | 10 July 1941 | data-sort-value="September 1943" | surrendered at armistice September 1943 | ||
| CRDA | 7 August 1941 | data-sort-value="9 November 1942" | torpedoed 9 November 1942 by | ||
| OTO | 12 April 1942 | data-sort-value="September 19433" | surrendered at armistice September 1943 | ||
| OTO | 1 June 1941 | data-sort-value="September 1943" | surrendered at armistice September 1943 | ||
| CRDA | 23 August 1941 | data-sort-value="6 December 1942" | torpedoed 6 December 1942 by | ||
| Tosi | 9 November 1941 | data-sort-value="September 1943" | scuttled at armistice September 1943; raised by Germans, sunk in Allied air raid 1944 |
Of the 13 vessels completed, eight were lost in action. The submarines served in the Mediterranean.