Lead Chromate Pigments and Turkey

Lead Chromate Pigments and Turkey

Abstract

While the use of lead chromate pigments, simply denoted by the formula PbCrO₄, has been restricted in developed countries, Turkey has experienced a sharp increase in their consumption in the opposite direction. Defined as a hazardous product due to their components classified as environmental pollutants and carcinogens, these pigments were previously sourced primarily from European Union countries. Following their ban in those countries, sourcing has shifted to countries such as India, Canada, Colombia, and others. This article presents their imports over the years while recommending the use of environmentally compatible organic pigments as a replacement.

Introduction

Lead chromate pigments, roughly represented by the chemical formula PbCrO₄, were first produced synthetically in 1809 (1). Synthetic lead chromate pigment, synthesized by a French chemist named Louis N. Vauquelin, entered commercial use only in the 1920s. Due to relatively high light and weathering fastness properties, it became widely used as a standard in school buses and taxis in the United States for a long period. In Turkey, the primary pigment in Taxi Yellow remains largely lead chromate-based. Lead present in lead chromate is a heavy metal that is highly polluting to the environment. Another component in the pigment, Cr, is a much more polluting and carcinogenic substance. Due to these properties, the United States and the European Union have banned the use of lead chromate pigments.

Turkey's Lead Chromate Pigment Imports

When I started work in the paint industry in 1993, the first words I heard from pigment manufacturers attending technical meetings were that lead chromate pigments had reached the end of their lifespan and their use would soon cease, and therefore they should be replaced with organic pigments at the earliest opportunity. Turkey's annual imports of lead chromate pigments in US dollars and tonnes are compiled from the Foreign Trade Statistics database of Biruni TUIK and shown in Figure 1 (2). At the beginning of the 2000s, lead chromate pigment imports valued at USD 1.5 million and averaging around 500 tonnes entered a period of rapid increase from 2005 onwards, as can be seen in Figure 1, reaching USD 9.2 million in 2013. In terms of volume, the maximum volume level was reached in 2013 at 2,000 tonnes. From 2015 onwards, imports have fluctuated between USD 6 and 7.6 million annually. In terms of volume, annual imports have ranged between 1,650 and 1,850 tonnes. Until 2007, lead chromate pigment imports were led by European Union countries; the share of EU countries declined until 2019, when it completely ceased. In contrast, Canada increased its exports of lead chromate pigments to Turkey from 2007 onwards, reaching peak levels in 2019. The most important reason for this increase is CIBA's transfer of lead chromate production to a Canadian company. However, in recent years, Canada's exports have shown a continuous decline, likely due to financial constraints. As European Union countries began to slow down and stop lead chromate pigment production, imports from India began to increase from 2010, immediately following Canada. Indian-sourced imports, which exceeded 760 tonnes in 2010, peaked in 2022 at 1,083 tonnes and USD 4.4 million. Following NUBIOLA's, now part of FERRO, shift of its production in Spain to Colombia, Colombia became the third country exporting inorganic pigments to Turkey. China is the fourth largest country in Turkey's lead chromate imports. China's exports reached USD 870 thousand in 2020. [caption id="attachment_157703" align="aligncenter"] Figure 1. Annual import values and volumes[/caption] During the first 10 years of the 2000s, lead chromate pigment was imported from around 30 countries to our country; today this number has fallen to 6-7 countries. The current leading countries, ranked by export size, are India, Canada, China, and Colombia. Lead chromate pigments are imported from seven main sources in India, there are 2 suppliers from China, and 1 producer each from Canada and Colombia. I believe it is wrong that the use of lead chromate pigments, which was at an average level of 500 tonnes at the beginning of the 2000s, has been reduced to zero in developed countries while rising to 1,800 tonnes in Turkey. The fact that a significant portion of these pigments is used in road marking paints poses a considerable environmental risk. The annual production and use of road marking paints with approximately 400–500 tonnes of lead chromate pigment additive results in lead chromate pigment dust mixing into nature at this rate every year. Despite this high consumption, lead chromate pigment use has completely ceased in masterbatch, particularly those used in thread production, and to a large extent in powder coatings production. However, as mentioned above, lead chromate pigments are still used in road marking paints, various automotive repair and industrial paints, and plastic masterbatch colorization. In construction paint production, there may be limited use in second-quality products. Furthermore, it is unknown whether lead chromate pigments used in masterbatch production are used in toy colorization.

Lead Chromate Pigment Types and Organic Alternatives

Lead chromate pigments are pigments with Colour Indices PY 34 and PR 104, and their contents are given in Table 1: • PY 34: Lead Chromate (Primrose, Lemon & Medium) PbCrO₄ / Pb SO₄ • PR 104: Lead chromate/Lead Molybdate: PbMoO₄ [caption id="attachment_157704" align="aligncenter"] Table 1. Lead Chromate Types and Contents[/caption] Colour indices of organic pigments that can be recommended as alternatives to lead chromate pigments: • For Decorative Paints: PY 74, PY 83, PY 42, PO 34. • For Industrial Paints: PY 42, PY 139, PY 151, PY 154, PO 36. • For Plastic Colorization: PY 13, PY 83, PY 139, PY 151, PY 154, PY 191, PO 34.   References (1) LJH Erkens, H Hamers, RJ Hermans, E Claegs, M. Bijnens, "Lead chromates: A review of the state of the art in 2000", Surface Coatings International Part B: Coatings Transactions, Vol 84, B3, 169-242, July 2001 (2) https://biruni.tuik.gov.tr   Assoc. Prof. Gürses Öner Regional Sales Manager Sudarshan Chemicals Industry Ltd.