Global use of lead chromates has significantly declined in recent years due to the pigments’ toxicity. In the past decade alone the quantity used has declined by more than half, down from 90,000 t in 2000.1 However, due to the excellent price/performance of lead chromates and the partial use of the pigments in color mixing systems, complete replacement has failed to occur so far. The recent approval requirement for REACH annex XIV in May of 2015 has again increased the focus on the issue of alternative formulation concepts.
Lead chromates are typically used to achieve good hiding power with a high brilliance level in paint films. In fact, so far there is no individual pigment alternative for an exact 1:1 replacement of specific chrome yellow P.Y. 34 or molybdate red P.R. 104 pigments. The reformulation of such a formula is still a challenge, even for application technicians with coloristic experience. Color formulation using multiple pigments is the current state of the art. Pigment combinations, hybrid pigments and customized pigment preparations are already being used successfully as alternatives to lead chromates. Classic pigments for such combinations include P.Y. 74, P.Y. 83, P.Y. 139, P.Y. 151, P.Y. 154, P.R. 112 and P.R. 254 as organic components, and P.W. 6, P.Y. 53, P.Br. 24 and P.Y. 184 as inorganic components. In these combinations, the inorganic component contributes to achieving the hiding power, while the organic component is used to adjust the hue angle, chroma and color strength.