Use of LCA to evaluate the environmental benefits of substituting chromic acid anodizing (CAA)

Abstract

Chromic acid anodizing processes are currently being replaced in many industrial sectors because of the recognized adverse effect on the environment and health of used hexavalent chromium compounds. The environmental impacts of the existing processes must, however, be quantified in order to constitute a baseline against which the environmental performance of potential alternative options could be compared. The whole life cycle of the process should also be taken into account to ensure that the possible chosen solution for eliminating or lowering chromium (VI) emissions would not drastically damage the overall process performance in other environmental areas. In our study, we used a simplified life cycle assessment methodology that only took into account the key environmental issues of the considered industrial sector. Both the scope and the data needs were reduced by focusing only on significant flows and by using a generic database for steps other than the anodizing one. A precise literature review was carried out to evaluate bath atmospheric emissions. The results of the performed assessment confirmed that the only way to efficiently deal with hexavalent chromium compounds is to substitute the electrolyte used in the bath as the most Cr(VI) emissions are caused by other stages than the main one. Other specific issues, such as water and energy consumptions have, nevertheless, to be studied throughout the whole life cycle of the chemical substitute to monitor performance against CAA.Chromic acid anodizing processes are currently being replaced in many industrial sectors because of the recognized adverse effect on the environment and health of used hexavalent chromium compounds. The environmental impacts of the existing processes must, however, be quantified in order to constitute a baseline against which the environmental performance of potential alternative options could be compared. The whole life cycle of the process should also be taken into account to ensure that the possible chosen solution for eliminating or lowering chromium (VI) emissions would not drastically damage the overall process performance in other environmental areas. In our study, we used a simplified life cycle assessment methodology that only took into account the key environmental issues of the considered industrial sector. Both the scope and the data needs were reduced by focusing only on significant flows and by using a generic database for steps other than the anodizing one. A precise literature review was carried out to evaluate bath atmospheric emissions. The results of the performed assessment confirmed that the only way to efficiently deal with hexavalent chromium compounds is to substitute the electrolyte used in the bath as the most Cr(VI) emissions are caused by other stages than the main one. Other specific issues, such as water and energy consumptions have, nevertheless, to be studied throughout the whole life cycle of the chemical substitute to monitor performance against CAA

LCA to Evaluate the Environmental Impact for Chemical Pre-treatment in Plastics Metallization

“…LCI data for chromium anhydride were obtained from Harscoet and Froelich [3], and Kowalski et al [23]. Chromium trioxide can be produced by mixing sodium dichromate with sulphuric acid in a reactor heated externally and stirred with a sweep agitator.…”

“…The evaluation of the environmental benefits of potential alternatives may be accomplished using the Life Cycle Assessment (LCA) methodology. A previous study done by Harscoet [3] highlighted the environmental impacts during the production of chromic acid and the chromic acid anodising. Few studies have been performed to analyse the impact of substitutes for chromic acid anodising: Serres et al [4] and García et al [5] have assessed the substitution of hard chromium with thermal spray and laser techniques; Benveniste et al [6] compared energy requirements and some environmental burdens for ceramics Physical Vapour Deposition, SiO x Plasma and Chromium electroplating; and Jugy et al [7] compared electrochemical process for the anodising treatment of aluminium against corrosion with and without chromic acid.…”

Thermal curing study of bisphenol A benzoxazine for barrier coating applications on 1050 aluminum alloy

“…Nevertheless, these alloys are susceptible to localized corrosion [1][2][3] and, therefore, need to be protected. Several coatings are commonly used at an industrial level in order to improve their corrosion resistance such as anodizing layer [4], conversion coating [5] and organic coatings [6]. In most cases, these coatings are chromate-containing layers [4][5][6], showing excellent anti-corrosive performance.…”

“…Several coatings are commonly used at an industrial level in order to improve their corrosion resistance such as anodizing layer [4], conversion coating [5] and organic coatings [6]. In most cases, these coatings are chromate-containing layers [4][5][6], showing excellent anti-corrosive performance. Due to the high chromate toxicity for human beings and environment, the use of these compounds will be banished in 2017 in the aircraft sector.…”

A quantitative determination of the polymerization of benzoxazine thin coatings by time‐of‐flight secondary ion mass spectrometry

“…Aluminum alloys commonly used in aeronautical industry are sensitive to localized corrosion. At the industrial scale, several pretreatments are currently developed to enhance the anticorrosion properties: anodized layers, conversion coatings, and organic coatings . However, the anodization protection pretreatment usually involves highly biotoxic chromates, which are progressively banned since September 2017.…”