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Tartaric-sulfuric acid anodizing

Quickstart:
     Readers wanting a quick understanding of aluminum anodizing may wish to start with our "Aluminum Anodizing: Intro & FAQs".
     Type 3 anodizing, designed for thin coatings and non-corrosive residuals, has been traditionally based on chromic acid. But concern over the toxicity of chromic acid, and it being effectively forbidden by European RoHS and REACH standards, has led to substitutions including tartaric-sulfuric acid (TSA) anodizing.
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(this entry appended to this thread by editor in lieu of spawning a duplicative thread)
Q. What is TSA Anodising, who introduced it, who will provide certificate to implement it in a company, what is the composition?

Naushad Pasha
employee - Bengaluru, India
February 13, 2026

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⇩ Similar, related, Q&As -- oldest first ⇩

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Q. tartaric acid ⇦ on eBay or Amazon [affil link] anodizing (TSA) and boric sulfuric acid anodizing (BSAA) are developed as alternatives to chromic acid anodizing due to REACH regulations. We are looking for an alternative to chemical conversion coating meeting the requirements of MIL-DTL-5541 [⇦ this spec on DLA] and MIL-DTL-81706 [⇦ this spec on DLA] .

For the being time, we are using Alodine 1200s. Alodine 1200s is insulating material itself, however when we apply to Aluminum surface thin layers, we obtain Class 1A and Class 3 coatings according to MIL-DTL-5541 where the parts are conducting electricity.
My question is: if we apply thin layers of TSA or BSAA can we obtain Class 1A or Class 3 parts?
Thank you in advance

AYSUN AKIN
ENGINEER - ANKARA, TURKEY
October 30, 2008

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Q. I hope someone can help. Our company has been asked about converting to tartaric acid /sulfuric anodising from Chromic acid anodising due to our customers desire to comply with the European REACH legislation. As REACH relates to 'substances of concern' being present in the finished article, then is there any Chromate in the surface of a component that has been chromic acid anodised? If not, then surely the REACH legislation should not apply to CAA finishes.
Thanks in advance for any response given.

Mark Lees
company chemist - Isle of Man, British Isles
February 24, 2010

A. Yes, CAA has chromate in the finish, however, for REACH compliance you may be able to claim an "article exemption". Read more about REACH as it applies to metal finishing here: https://www.nmfrc.org/compliance/reach.cfm ⇩ Tartaric-sulfuric acid anodizing and boric-sulfuric acid anodizing are both replacement chemistries aimed at eliminating the chrome of chromic anodizing. It may make business sense to switch to one of these processes anyway rather than try to achieve an article exemption under REACH. BSAA is much more of a tried & true process by many shops in the U.S. compared to TSAA. There is one more thing to consider. A switch to TSAA or BSAA doesn't necessarily ensure REACH compliance as those coatings, last time I checked, still relied on a dilute chromate seal. Jon Barrows, MSF, EHSSC Independence MO Ed. update 2026: The above link redirects to www.caiweb.com/shutdown.html, which advises that "... that content will no longer be maintained nor updated". Thankfully, the Internet Archive preserved a copy here  🙂 Please consider a donation to The Internet Archive. Never follow abandoned links or redirects to other sites! Because such links are found on trusted sites, hackers anxiously seek them for installation of malware onto your computer. A. Mark, I am assuming that someone has asked if any of your parts contain Substances of Very High Concern (SVHCs)at concentrations greater than 0.1% in accordance with Article 33 of the regulations. The current SVHCs listed that contain hexavalent chromium are the following: Sodium dichromate (both anhydrous and dihydrate) Lead sulphochromate yellow (C.I. pigment yellow 34) Lead chromate molybdate sulphate red (C.I. pigment red 104) Lead chromate Chromic acid anodising utilises chromium (VI) oxide and is not currently listed as a SVHC and so does not need reporting. Even if some of the chromium (VI) oxide was left on the surface, it still doesn't come under the reporting requirements of REACH. I will say that I expect chromium (VI) oxide to be included in one of the next two or three SVHC lists (currently being published annually), so it will only be a short stay of execution before it does come under Article 33 reporting requirements. Brian Terry Aerospace - Yeovil, Somerset, UK

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Q. There is talk of a tartaric acid-sulfuric acid solution that is being tried. If anyone can give me a procedure for the analysis of the total acid by titration with the use of a burette I would be very happy. ⇦ Answer?

Michael Boissinopt
Electro plating - Southend Essex, United Kingdom
May 20, 2010

Q. Currently having to set a Chemical Analytical Laboratory from scratch to help support the new anodising production line which is not installed yet.
Cannot find any standard methods to analyse Tartaric Sulfuric Acid bath and maintain the pH.
Has anyone got any methods to analyse the solution? ⇦ Answer?

Anthony Hopker
- United Kingdom
May 15, 2012

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