MULTISTAGE PRETREATMENT OF TINPLATE PRIOR TO THE COATING THEREOF WITH LACQUER

摘要

The invention relates to a two stage method for the anti corrosive pretreatment of tinplate in which an anti corrosive primer coating is already applied in a first step said primer coating effectively preventing the shiny metal surface of the pretreated tinplate from turning black when the pretreated tinplate of the invention that is provided with a coating lacquer is in contact with liquids containing or releasing sulfur compounds and with food containing protein. In the disclosed method the tinplate is anodically polarized in an electrolyte containing at least one inert water soluble salt and is then brought in contact with an acidic aqueous composition containing water soluble inorganic compounds of the elements Zr Ti Hf and/or Si. Tinplate pretreated according to the invention can be used in particular for the production of food safe packaging such as beverage cans or tin cans.