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Olive drab chromating on zinc plating sometimes goes yellow

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We have acid zinc and chromatized olive drab. The problem is that some pieces has both color after chromatized olive green and yellow. We made a X-Ray spectrum in both areas (green and yellow) but the spectrum are similar in both cases. The bath hasn't got metallic contamination.

Help us, please.

Enrique Bustos
- Cordoba, Argentina

You really need the help of your supplier but Check Cr6 conc and adjust. Prob too high Check pH In a bucket try adjusting pH with the recommended acid -prob sulfuric and also try modifying concn of Cr6 Always do this in a small quantity test first as it is easy to muck up a tank by going the wrong way.

Geoffrey Whitelaw
- Port Melbourne, Australia

Me gustaria me comentaseis el problema en castellano por si pudiese ayudaros, ¿creo entender que el pasivado verde os sale amarillo?

Un Saludo,

Miguel Angel Martín
surface finishing shop
Madrid, Spain

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