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Ted Mooney, P.E. RET
Pine Beach, NJ
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for Metal Finishing since 1989
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How to Mask for Hardcoat Anodize
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Q. Hello Guys,
I'm a chemical engineer and recently working on aerospace parts which requires both Type III Hard Anodizing and Type I CAA, that some area requires Type III and other area requires Type I.
We have problem on arranging these 2 anodize processes, like which would be the first while facing some masking issue.
But by chance I heard that this could be achieved by first anodizing with Type I on the whole surface of part, then mechanically remove the area to be anodized for Type III, finally direct anodize the part for Type III, without any masking on the anodized type I coating.
Do you guys have any experience on this method and I'm also concern about does the further hard anodizing with sulfuric acid have any bad effect on the type I CAA coating?
looking forward for your reply and have a good day!
- Shreveport, Louisiana
January 11, 2022
adv.
Yuri, I believe that we can help you with this problem. Please give us a call at 888-218-7227. www.maskcoat.com
Jeremy
Mask Coat LLC
West Monroe, Louisiana
⇩ Related postings, oldest first ⇩
Q. Help! :-)
My company manufactures aluminium prismatic components for the aerospace industry. We currently employ a brown wax mask in order to prepare parts for the hard anodizing process. However, the application and removal of the wax is time consuming and is thought to be causing acid attacks on the component during its removal.
Can anybody out there recommend an improved mask that may assist us?
Many thanks for your time.
- Wolverhampton, England
2002
A. Ian,
Check if your folks 'reuse' the wax by putting the wax from the de-wax tank back into the wax tank. If they do you may well of found your problem. We use wax and have no problems, but we never 'reuse' the wax and never put wax removed from cut back operations back in the wax tank.
Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England
A. Ian, apart from waxes there are organic resin "Stop-offs" available from most of the larger Metal Finishing Suppliers.
Good luck.
Melbourne, Victoria, Australia
Thanks for your help guys.
- England
A. Chromic Anodize or Type II conventional sulfuric acid anodize first, seal very well, grind off the areas to be hard coated, then hard coat anodize. The chromic acid anodizing will mask adequately. AES Proceedings 1958, Dr Harold Weisner then of Bendix Kansas City.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
A. Have you tried to use a masking disc, such as aluminum or lead foil discs? They can be cut to shape and will hold up well in your process. There are various polyester and vinyl tapes that can also do the job, though the quality of the vinyl is important, and the cost of polyester can be prohibitive.
Ty Sarajian- Brookfield, Wisconsin
Q. I am a Sales Engineer working in the Anodizing Field. I am working with a customer who is doing Hard Coat Anodize. We are looking for a product to dip the parts in to mask & then cut away what area we need hard coat anodized. We tried one masking supplier, and too hard to remove masking (not an option). Does anyone have any suggestions how to mask a medium size part entirely & then cut out a small groove to be hard coated? Thanks for the input!
Cliff ShephardSales Engineer - Charlotte, North Carolina
2004
A. Basically, there is no dip process that will not have some anodize thru thin spots or pores and still be "easy to remove". Wax is an option, but not a good one. It would help if you could be a little more specific about the part. Medium sized means something to only you. Why not send a picture with a couple of dimensions?
Also, which product did they try. While that product may not have been satisfactory to your user, there are a number of similar products that also will not work. With no idea, how can anyone comment. I do not think that Ted will mind a brand name in this case as it will be more generic than specific. Especially since you have not said that it was bad, just that it did not fit a client's particular need. There might be other masking alternatives than a dip process.
- Navarre, Florida
Ed. note: the maskant which was tried was a Tolber product but Mr. Shephard did not advise type or number.
A. Put down some tape where you want the anodize; mask the part; cut the mask along the sides of the tape; peel off tape. You may need a strong tape depending on the mask material. Either Kapton or glass-cloth tape are some that come to mind.
Tom Gallant- Long Beach, California
A. Cliff,
I don't know if this will be an option for you but it is something I know that works. First of all realize that there is no good masking for anodize of any type.
Begin by chromic acid anodizing the part all over and seal with nickel acetate. Use any convenient method, i.e., tape, wax, thermocote, paint, to mask off the areas not to be hardcoated. Remove the chromic acid anodize by etching and Hardcoat as normal.
If the chromic anodize in the hardcoat area is skim cut by machining then no other masking material would be needed. The sealed chromic anodize will act as the mask.
Tim Hamlett, CEF
- West Palm Beach, Florida, USA
Q. Hello,
I am a tool designer for a company in the States that specializes in making precision molded products for selective surface treatment. Aviation in particular is our bread & butter. I just happened to stumble on this thread. I apologize for being vague or if this post is invasive but I just did not see any recommendations for custom hard tooling in the responses.
Regards,
- Avon Indiana
February 4, 2010
Q. HOW CAN I PROTECT ALUMINUM FROM HARD ANODIZE(TYPE 3) USING CHROMIC ANODIZE(TYPE 1)?
ALI GHANEMPLATING SHOP EMPLOYEE - ISRAEL
December 8, 2010
Using Chromic Anodising as a maskant for Hard Anodising
Treatment &
Finishing of
Aluminium and
Its Alloys"
by Wernick, Pinner
& Sheasby
(note: this book is two volumes)
on eBay or
AbeBooks
or Amazon
(affil links)
Q. Hi Guys
We currently use wax as a selective mask prior to hard anodise of 2000 series aluminium aircraft components, however this is a time consuming process as the parts are complex. We are looking at trying to use chromic anodising as a maskant prior to hard anodise instead. i.e. chromic anodise all over, skim the bore to bright metal, then hard anodise. Does anyone have any experience of this process?
Any advice would be much appreciated.
Thanks in advance.
Barry
Manufacturing engineer - Birmingham, UK
June 21, 2016
|
A. Wax for hard anodise process? Hi Barry can you recommend a supplier of the low temperature wax in the UK please. alan clayton- chester February 10, 2023 A. Hi Alan. I wish we could let people answer questions like that and post testimonials, but 33 years on line and a quarter million postings has proven that we can't ( huh? why?) :-( Sorry! |
A. Hi Barry. That approach is common, and we have appended your question to one thread which addresses it. It is also mentioned in letter 14483. Good luck
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi Ted
Thanks for your response. In one of your letter links Robert H. Probert outlines the process and references "AES Proceedings 1958, Dr Harold Weisner, then of Bendix Kansas City". Probably a long shot, but would you know how to find a copy of the relevant section of these proceedings?
Regards
Barry
Manufacturing Engineer - Birmingham, UK
June 23, 2016
Aluminum How-To"Chromating - Anodizing - Hardcoating"
by Robert Probert
Also available in Spanish
You'll love this book. Finishing.com has sold almost a thousand copies without a single return request :-)
A. Hi Barry. You could ask Robert; it wouldn't surprise me if he had a copy rather than a memory of a 50+ year old paper. You could inquire of www.nasf.org but I doubt they retain proceedings of that age.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Hi,
We trialed this method on test discs using chromic acid anodise as a mask. It was not a complete success. I suspect the hot DI water seal we used was the issue. We trialed each of 4 discs at 8, 15, 25 & 60 minutes seal respectively with varying levels of success. The first three all had small spots of hard anodise all over the chromic anodise with varying frequency. The last one had a very light film of it in patches. Question - could anyone advise if another type of hot seal i.e. nickel acetate would do better? Any advice would be much appreciated.
Barry
Manufacturing Engineer - Birmingham, England
A. Yes, Alcoa also said in 1956 Aluminite book, that hot water over 15 minutes deteriorates the coating, and I cannot persuade the Mil spec writers to change it. Boeing recognized this problem and came out with their dilute chromate seal. Alcoa also said in 1956 that the hot water does not deteriorate if a very small amount, they said how much, of chromic acid is added to the seal. Any way, it is still very difficult to get the coating sealed well enough to withstand the hard coat condition. If you will send your address, I will go to the copy store and copy several pages of Dr. Weisner's paper. He first presented the paper in an Atlanta AES conference in 1958, and again later at the national convention. And I had dinner with him that night. No better paper on hard coat has ever been published.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
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