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Tartaric-sulfuric acid anodizing

October 30, 2008

Q. Tartaric acid 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 [affil. link or DLA] and MIL-DTL-81706 [affil. link or 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


November 5, 2008

A. Aysun,

Anodising is not conversion coating and so will not meet the requirements of MIL-DTL-5541 [affil. link or DLA] regardless of class.

What you need to do is talk to your customer and see if they would consider TSA or BSAA as a replacement for the MIL-DTL-5541.

The other possibility, if it is allowed by your customer, is to try the non-chromate conversion coatings. Again make sure you communicate with your customer at all times as this will involve a design change and could potentially affect the functionality of the part.

Brian Terry
Aerospace - Yeovil, Somerset, UK

February 24, 2010

Q. I hope someone can help. Our company has been asked about converting to Tartaric acid/sulphuric 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

simultaneous February 25, 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
Jon Barrows, MSF, EHSSC
GOAD Company
supporting advertiser
Independence, Missouri

February 26, 2010

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

 May 20, 2010

Q. There is talk of a Tartaric Acid Sulphuric 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.

Michael Boissinopt
Electro plating - Southend Essex, United Kingdom

May 15, 2012

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?

Anthony Hopker
- United Kingdom

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