ASTM D Standard Recommended Practice for Preparation of Metal. Surfaces for Adhesive Bonding. ASTM D Standard Guide for. D – Designation: D – 98 AMERICAN SOCIETY FOR TESTING PA Reprinted from the Annual Book of ASTM Standards. D, Method r, and ASTM E involves the etching of aluminum dure is described in ASTM D and involves the application of.

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I am looking for technical information on PAA phosphoric acid anodizing. I have searched the web and cannot find much technical info. Do you know where I can get the info? I am trying to asm up a small bench top operation. I run a small job shop and I’m just seeking to help r3933 customer out while he does some samples for adhesive bonding tests. Minford from Abe Books or info on Amazon A. Phosphoric acid anodizing is porous and provides a substrate for mechanical locking, so I suppose that is why you need s3933 for the adhesion test.

The specification for the adhesion test should have the parameters you need for applying the anodic coating. It is reference book time. Take a look at this sites “must have” book list. Very straight forward and the cheapest good reference.

There are better, but cost a lot more. James’ recommendation was fromand even then the “Light Metals Finishing Process Manual” was quite hard to find. If you see an affordable copy anywhere e3933 days, grab it: There is very little information on this specialized process.

I know of two methods: The first is used by Boeing for adhesive bonding. Anodize at ASF for minutes.

Phosphoric acid anodizing per BAC5555 and ASTM D3933-98

You may be looking for Boeing’s BAC process. You may find something on the web under PAA or BAC, or you can do a literature search which will give you some data, or consider contacting Boeing’s commercial development office about licensing BAC I am trying out Phosphoric Acid anodizing for a new customer. Can you help me with a process for Phosphoric acid anodizing. My customer requires this process as they need to atsm for another bonding process. To make more info available with less searching, we’ve combined together onto this page a number of previously separate threads about phosphoric acid anodizing.

Please send contact information, I’ll forward drawings for an RFQ. Need a source for PAA etch to D [link by ed.

Standard Guides for Automotive and Aerospace Adhesives from ASTM

I have just quoted a d39333 phosphoric anodize job. My main question is what is the recommended cathode material for this chemistry? Thank you in advance for your help.

Phosphoric acid anodizing is done with stainless steel cathodes. If the anodizing tank is stainless steel, the tank itself can be the cathode. Phosphoric acid anodizing is usually requested by the aerospace industry. It is used as a surface preparation for bonding. There are very stringent requirements for application and inspection of phosphoric acid anodized parts [for wstm application].

Usually the customer requires a certification before parts can be processed. People in our composites group are pushing the electroplating facility to install a phosphoric anodizing process to prep aluminum for adhesive bonding.

Can anyone tell me what equipment is needed to phosphoric anodize aluminum? I need info like tank liners, cathode material, voltage and amp requirements, bath temp, etc.


We appended your question to a thread which should answer many of your questions without having to wait for replies. Phosphoric acid anodizing PAA is used to give aluminum a good tooth for adhesive bonding. See D [link by ed. My understanding is that some of Boeing’s competition does not use this process for adhesive bonding, but rather a variant of chromic acid anodizing.

I am currently setting up a phosphoric acid anodize PAA line. PAA is used to prepare the aluminum surface for acceptance of the primer before bonding.

You should note that PAA specifications call for the anodized parts to be stored in a “clean room” environment prior to application of the primer.

Parts must be transferred to the clean room within two hours of removal from the PAA line and be primed within 72 hours. After priming, parts can be stored before bonding. Now maybe there are some issues that are addressed inside of NASA that I am not aware of obviously, but I don’t see the reasoning behind phosphate coating over chromate. Chromate can withstand and in some cases mostly material dependent I have seen in cases it pass hours. I’m not saying phosphoric cannot do this, but why open up a potential can of worms if you can achieve your goal and avoid some headaches.

Joel, there are some very specific requirements concerning bonding using PAA. There is an engineering document you need to be qualified to for Boeing work. I would suggest starting there with some of the engineering requirements then go to the PAA spec. Prior to engineering your line you may wish to also think about production flow logistics as Ray mentioned which are critical for best results, as well as meeting most aerospace specs.

I cannot talk about certain Boeing processes on an Internet website for obvious reasons but would be glad to speak with you in person if you wish. Stiltner, the answers to your questions are partially in the two volume set by Wernick, Pinner and Sheasby, The Surface Treatment of Aluminum and its Alloysand a number of books on pretreatments of aluminum for bonding purposes.

If you are interested, one I might suggest is Surface Prep. Techniques for Adhesives by R. Wegman published by Noyes publications. Another would be Handbook of Adhesives edited by Skeist.

Basically there are some particular surface phenomenon characteristics with PAA which are not acquired elsewhere other than possibly FPL etches, and that could be arguable. Ted is right that some adhesive bonding is performed using CAA as an alternative to PAA, but my understanding is the lap shear test comparisons do not show the same results over time. When we wrote it some years ago, it contained just about everything we wanted for aerospace structural adhesive bonding.

Surely, since the original document was written, there have been advances in structural adhesive bonding. However, many of the basic tests and ideas for quality control, etc. If Boeing’s BAC spec is still active, then it would be prudent to consider it’s use. The Mil spec was written to get people to use stressed, environmental testing for adhesive bonding quality control instead of relying only on plain lap shear tests and to use good overall practices.


At that time, Phosphoric Anodizing was best for most structural adhesive bonding. Chromic acid and other anodizing methods, while good for corrosion protection, seldom proved in environmental stress tests, e. In addition, clad aluminum bonded parts corroded in the clad layer, thus releasing the bond.

If you want a quick and dirty demonstration, make standard peel test specimens from candidate surface preps. Start pulling them apart by hand careful of sharp edgesthen put a drop of water d933 the joint.

You MAY be surprised by the result. It is not clear to me if Phosphoric Acid Anodizing is still patented or not.

Standard Guides for Automotive and Aerospace Adhesives from ASTM

I don’t know if the patents have run out on BAC or not — you’d have to do a patent search. Sorry for the non-definitive answer. What are the surface phenomenon characteristics of PAA that make it so desirable for adhesion? Also, are there any alternative platings that can produce the same results?

Hi, Asym and Jeff. I am not an aircraft engineer and cannot give you an authoritative answer; but maybe this help you until someone more knowledgable steps forward. PAA and Chromic acid anodizing are thin coatings which I wouldn’t expect to have nearly the bad effect on asrm strength that much thicker coatings like sulfuric anodizing have, yet they are somewhat porous and adhere to the substrate well, while being corrosion resistant.

Hello, I am working on a Epoxy joint on Aluminium. So I am now looking for the BAC to get more information. The spec can be obtained from Boeing commercial division or from some specification clearing houses like aerospheres. I am working at a US Air Force base. It uses sulfuric acid anodizing at many sites, and has a phosphoric acid anodizing operation astj one building. It is then sealed using DI water in a series of two dip tanks.

The phosphoric acid anodized sheets are then d933 bonded. We could more easily recycle the waste anodizing solution is we could convert the phosphoric acid anodizing bath to sulfuric.

Is there any literature about the advantages and problems associated with switching from phosphoric acid to sulfuric acid anodizing? Will it require a different sealer, such as with sodium chromate? We have been satm that the sulfuric acid process is more temperature sensitive, and we might have to install a chiller and a heat exchanger to control the temperature. The main office, downtown, used to have one of the ashm libraries going.

Phosphoric anodizing is well known as being superior to sulfuric acid for bonding purposes. I rather doubt if the gain is waste treatment is worth the reduction in bondability. That is a aastm decision. What is the temp of those tanks?

Nonetheless, if the PAA is being called out astn a pretreatment for a subsequent pressure bonding operation than the answer is no, sulphuric acid anodizing is not the coating of choice for a variety of reasons. The only other anodize treatment called out for bonding prep work is CAA which now brings Hex Chrome into your facility.