Lead-chromate pigments

Bismuth V n d te. The use of lead chromate pigments has been slowly phased out of many appHcations. Thus a search for more environmentally acceptable relatively inexpensive yeHow pigments having exceHent coloristic properties has been ongoing. 

The basic compositions of the most common commercially available lead chromate pigments are given ia Table 2 (44). 

The principal producers of lead chromate pigments ia North America are Cookson, DCC (owned by Kikuchi), Engelhard, and Wayne Pigment. In Europe, lead chromates are produced by Ciba ia Holland, CapeUe ia Erance, and Heubach GmGH ia Germany. 

The 18 substances are shown in Table 1. Five of these substances are now (June 2012) included in Annex XIV (Authorisation list) [29]. These substances are the lead-chromate pigments, pigment yellow 34 and pigment red 104, and the phthalates DEHP, DBP and BBP, which all are used as components/additives in some printing inks. As evident from Table 1, cobalt(II) salts and trichloroethylene appear on the Annex XIV candidate list [28], and they are also used as additives in some printing inks. ECHA has recommended in its third recommendation [30] to put these two substances on the Authorisation list [29]. Besides these seven substances of very high concern (SVHC substances) appearing on either the Authorisation list or its candidate list, 11 other substances that meet one or more of the criteria for the candidate list are shown in Table 1. These substances are also... 

Under certain conditions, dry mixtures of lead chromate pigments with the azo-dyes l-(2. 4 -dimtrobenzcncazo)-2-hydroxynaphthalene (dinitroaniline orange) or l-(4 -chloro-2 -nitrobenzcncazo)-2-hydroxynaphthalene (chlorinated para-red) may lead to violent explosions dining mixing/blending operations. 

Lead arsenates, 74 797 Lead azide, 70 727-729 74 792 Lead babbitt, 3 52, 52t arsenic addition to, 3 271 Lead-base babbitts, 24 797 Lead-based paint, 74 765 Lead-based paint remediation, 18 75 Lead-based pigments, 79 386. See also Lead chromate pigments Lead benzoate, 74 794 Lead bisilicate, 74 796 Lead blast furnace, 74 737 Lead borate, 74 797 Lead bromide, 74 785 Lead bullion, 74 742, 745... 

Lead chromate pigments, 19 405, 407-408 Lead Chromate Yellow, pigment for plastics, 7 370t... 

The presence of lead and hexavalent chromium in these products is of chronic hazard concern and the EU has classified these pigments as harmful substances. Lead is soluble at stomach-acid concentrations and can accumulate in the organism. The results of a high lead intake include inactivation of enzymes and disturbances in the synthesis of haemoglobin. Hexavalent chromium compounds are considered to be carcinogenic. For these reasons the usage of lead chromate pigments has declined considerably in recent years. 

Lead chromate pigments are not sufficiently fast to high sulfur dioxide concentrations. 

Lead chromate pigments are effected by materials containing sulfuric acid, such as soot or moist dead leaves, to which automotive finishes are frequently exposed. 

BASF produces temperature-stable lead chromate pigments with a silicate coating obtained by hydrolysis of magnesium silicofluoride [3.140]... 

Labelling. In the EC lead chromate and lead chromate pigments must be appropriately labelled. Such substances must be marked with a skull and crossbone (T) [3.158], [3.159]. Additionally, the following risk (R) and safety phrases (S) must be used ... 

Lead chromate pigments are not permitted for use as coloring materials for plastics for consumer goods [3.165], or for coatings for toys, according to European Standard EN 71 part 3 [3.166],... 

Lead chromate pigments are mainly used as corrosion inhibitive pigments. These pigments are of low opacity and can be combined with higher opacity pigments for use in primers. Zinc chromate, also an anti-corrosion pigment, is used in metal pretreatments such as wash primer, which also promotes adhesion to aluminum and steel. 

Lead chromate is almost insoluble and has very low bioavailability. Studies on lead chromate pigment have shown that it does not have the carcinogenic potential of soluble chromates, such as zinc chromate. As with other heavy metals, solubility is the key to toxicity. With proper safeguards such as adequate ventilation and personal protective equipment, chrome yellow and molybdenum orange can be safely used in the workplace. 

Lead chromate pigments, traditionally used for pipe and cable applications, are linked with the phase out of lead based stabilisers. Special pigment systems based on organic or organic/inorganic combinations are available (320). 

Precautions have to be taken and workplace concentration limits have to be observed when handling lead chromate and lead chromate pigments. MAK or Occupational Exposure limits for lead chromate and lead chromate pigments themselves are not given. 

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