Red Lead on Iron Ships

Scientific American 2, 9.7.1859

The most esteemed paint hitherto employed for the hulls of iron-ships has been red-lead, which was held to be very effective in preventing oxydization of the iron and the adherance of barnacles. We understand that this confidence in red-lead paint was based upon experiments made with it a number of years ago by eminent English engineers, but we learn from the Liverpool (Eng.) Albion that recent experiments go to establish quite a contrary opinion of its qualities. It seems that Mr. Robert Lamont was lately employed by the managers of one of the largest steamship companies in England to report on the merits of certain compositions used to a large extent in Liverpool for persevering iron-ships, and the fouling of their hulls, and the result of his investigations, recently reported, is quite contrary to the popular notion on the subject, as it is stated that red-lead is the most pernicious pigment that can be employed. An iron-ship, the William Fairbairn, which was coated with red-lead just prior to a recent voyage to and from Calcutta, had her plates corroded in such a manner that they attracted his especial attention. On a close inspection he found the red-lead coating covered with blisters, each of which on being opened, contained a clear fluid which left a number of clear crystals of metallic-lead, adhering to the iron. It is stated that each of these minute blisters was a miniature galvanic battery, which induced chemical action, hence the great extent of the corrosion in the iron, it being the most oxydizable metal, the lead being negative. He also states that the sweating to which iron-ships are subject, is caused in a great degree by the use of red-lead paint in immediate contact with the iron, and he therefore recommends that its use be abandoned for iron-ships.