chromic acid anodize per stp 58-209, ty i and br 127 2

[_LynseyJames]

Hi,

I'm very new to this business. Does anyone have any experience with companies that have the capability to process 7075-T6 Bare sheet metal with Chromic acid anodize per STP 58-209, Ty I and BR 127?


TIA,
Lynsey

 

[Sparweb]

The first page of hits on Google provide companies which offer their anodize processing to the STP 58-209 standard. And they all look valid.

What kind of "experience" to you mean to ask for?

Are you experiencing problems with the process in your facility, or problems with your suppliers?

 

[WKTaylor]

STP 58-209 Ty I is a company proprietary process... and may include chromic acid anodizing and BR127 [corrosion inhibitive adhesive bond-primer] application processes.

Odd that Your spec is applying chromic acid anodize [CAA] coating... instead of the more durable phosphoric acid anodizing [PAA] coating... in prep for adhesive bonding.

Typical CAA and sulfuric acid anodizing [SAA] and 'other' type chemistry... for corrosion protective anodize coatings ONLY... are typically applied per MIL-A-8625 [see spec for types] for corrosion protection.... rarely ever surface prep for adhesive bonding... but there is alot more to all of this than meets th'eye!

BTW: CAA process carries with it some pretty nasty-toxic and environmentally unfriendly chemicals and processes and may be prohibited in many localities. PAA and SAA do have 'their issues', but not to the great extent that CAA does.

You need to become familiar with aluminum surface-prep, application of anodic coatings and primer systems... in association-with/prep-for adhesive bonding.

Let me offer you a 'short list' of 'light reading' references... of the much longer list of info that I am intimately-familiar with...

ASTM D2651 STANDARD GUIDE FOR PREPARATION OF METAL SURFACES FOR ADHESIVE BONDING
ASTM D3933 STANDARD GUIDE FOR PREPARATION OF ALUMINUM SURFACES FOR STRUCTURAL ADHESIVES BONDING (PHOSPHORIC ACID ANODIZING)
ASTM D6465 STANDARD GUIDE FOR SELECTING AEROSPACE AND GENERAL PURPOSE ADHESIVES AND SEALANT

SAE AIR4844 COMPOSITES AND METAL BONDING GLOSSARY
SAE AIR4938 COMPOSITE AND BONDED STRUCTURE TECHNICIAN/SPECIALIST: TRAINING DOCUMENT.
SAE AIR5278 COMPOSITE AND BONDED STRUCTURE ENGINEERS: TRAINING DOCUMENT.
SAE AIR5279 COMPOSITE AND BONDED STRUCTURE INSPECTOR: TRAINING DOCUMENT.
...and numerous SAE AMS specs for various anodic processes...

MIL-A-83376 [CX] ADHESIVE BONDED METAL FACED SANDWICH STRUCTURES, ACCEPTANCE CRITERIA
MIL-HDBK-337 ADHESIVE BONDED AEROSPACE STRUCTURE REPAIR
MIL-HDBK-349 MANUFACTURE AND INSPECTION OF ADHESIVE BONDED, ALUMINUM HONEYCOMB SANDWICH ASSEMBLIES FOR AIRCRAFT
MIL-HDBK-961 ADHESIVE BONDING
MIL-HDBK-83377 ADHESIVE BONDING (STRUCTURAL) FOR AEROSPACE AND OTHER SYSTEMS, REQUIREMENTS FOR

MIL-PRF-8625 [MIL-A-8625] ANODIC COATINGS FOR ALUMINUM AND ALUMINUM ALLOYS

AFFDL-TR-77-135 PRIMARY ADHESIVELY BONDED STRUCTURE TECHNOLOGY (PABST) - DETAIL DESIGN
AFFDL-TR-77-107 PRIMARY ADHESIVELY BONDED STRUCTURE TECHNOLOGY (PABST) -GENERAL MATERIAL PROPERTY DATA
AFFDL-TR-79-3129 PRIMARY ADHESIVELY BONDED STRUCTURE TECHNOLOGY (PABST) - DESIGN HANDBOOK FOR ADHESIVE BONDING

USAF T.O.s
1-1A-1 ENGINEERING HANDBOOK SERIES FOR AIRCRAFT REPAIR - GENERAL MANUAL FOR STRUCTURAL REPAIR
1-1-8 APPLICATION AND REMOVAL OF ORGANIC COATINGS, AEROSPACE AND NON-AEROSPACE EQUIPMENT
1-1-691 CLEANING AND CORROSION PREVENTION AND CONTROL, AEROSPACE AND NON-AEROSPACE EQUIPMENT
1-1A-1 ENGINEERING HANDBOOK SERIES FOR AIRCRAFT REPAIR - GENERAL MANUAL FOR STRUCTURAL REPAIR


Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

 

[_LynseyJames]

Hi Sparweb, thank you for the reply.. We're not able to find a company that can perform the two processes together. For myself, I am one month into working for Topflight, my background is not aerospace. Thank you again for taking the time.

 

[_LynseyJames]

Hi WKTaylor,

Thank you so much for the reply, I am looking into the 'light reading' as we speak.

 

[Sparweb]

"perform the two processes together" - No, you must mean "sequentially" which is the only way to do both processes. Anodize must be complete before any primer can be applied. Furthermore, anodize may make the surface chemically inert or inactive to the bonding agents in the other primer process. Instead of "BR 127" which I'm not familiar with, have you considered selecting two different processes that are mutually compatible? Wil Talor's list is quite comprehensive, but I'll throw in MIL-C-5541 Chemical Conversion Coating, and MIL-P-23377D Primers to the list since they are still pretty common. You might not need the best-of-the-best-of-the-best.

For a little guidance on how different coatings perform, here's one:

https://apps.dtic.mil/sti/tr/pdf/ADA156927.pdf

 

[_LynseyJames]

Hi Sparweb,

Yes, you are correct. Sequentially is what I meant. It's all a very large learning curve for me at this time. I am taking in all the information that I am finding on this forum. I am so grateful for all this provided information. I believe due to our contract that is why are are looking for this exact treatment.

 

[WKTaylor]

BTW...

RE anodic coatings...

For best wear resistance and/or highest adhesion [epoxy adhesive-primer + epoxy-adhesive] DO NOT seal the anodic finish. This leaves the microscopic 'tooth' available for best grip on the primer system... hence the adhesive.

HOWEVER, for highest corrosion resistance, then SEAL the anodic finish and then apply a specific corrosion protective epoxy primer. Sealing the anodic finish encourages the growth/filling-in of the microscopic oxide-tooth to become a dense/non-porous film.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov