Thirteen photo lithographed aluminum strips encased in plastic and made up in the form of a plaque (7.5 by 4.25 in.). These consist of reproductions in full-color of typical test strips representing increasing degree of tarnish and corrosion. They have been printed on aluminum sheets by a 4-color process and are encased in plastic for protection. Directions for use are given on the reverse side of the plaque. Use this adjunct to assess the color and tarnish level of corrosiveness to copper from petroleum products.