Tinning

Introduction

Terne-plate is a similar product, but the bath is not of tin, but of tin and silversmith; terne-plates, which began to be produced in England about the middle of the 19th century are widely employed in the United States for roofing purposes.

History

The manufacture of tinplate was long a monopoly of Bohemia, but about 1620 the industry spread to Saxony. In 1665, Andrew Yarranton (1616-1684), an English engineer and agriculturist, was commissioned to go to Saxony and if possible discover the methods employed. According to his own account, he was very civilly treated and was allowed to see the whole process. On his return to England his friends undertook the manufacture on an experimental scale, but though they were successful they had to abandon it, because their method became known and a patent for it was trumped up by a rival, who, however, from lack of technical skill was unable to work it. Half a century later the manufacture was revived by Major John Hanbury (1664-1734) at Pontypool; the method of rolling iron plates by means of cylinders, said to have been devised by him, enabled more uniform black plates to be produced than was possible with the old plan of hammering, and in consequence the English tinplate became recognized as superior to the German. During the next hundred years or so the industry spread steadily in England and Wales, and after 1834 its expansion was rapid, especially in Wales, Great Britain becoming the chief source of the world's supply. In that year her total production was 180,000 boxes of 108 lb each (around 50 kg, in America a box is 100 lb), in 1848 it was 420,000 boxes, in 1860 it reached 1,700,000 boxes. But subsequently the advance was rapid, and the production, which was about 2,236,000 lb in 1891, had by 1900 increased to more than 849,000,000 lb, of which Over 141,000,000 lb were terne-plates. The total imports in that year were only 135,264,881 lb. In later years, again, there was a decline in the American production, and in 1907 only 20% of the American tinplate mills were at work, while the British production reached 14 million boxes.

Processes

There are two processes for the tinning of the black plates, hot-dipping and electroplating.

Electroplating

In electroplating, the item to be coated is placed into a container containing a solution of one or more tin salts. The item is connected to an electrical circuit, forming the ions in the solution are attracted to the item.

Hot-Dipping

In the hot dipping process, which is the older, the plates, after being properly flux, and by means of rolls the plates are passed through this down into the tin, to be brought out at another point in the bath where there is a layer of oil on the surface.

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.