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phosphoric acid etch for windscreen installation?

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CJohnston(at)popsound.com
Guest

Posted: Mon Sep 03, 2007 1:17 pm Post subject: phosphoric acid etch for windscreen installation?

hey all - 



what's the deal with this phosphoric acid etch stuff?  it says to do that before you install the windscreen fairing on page 45-18 step 9, but i have no idea what it means.  is there a special product you use to do this?  what the heck?



cj

phosphoric phool

do not archive

pitts_pilot(at)bellsouth.
Guest

Posted: Mon Sep 03, 2007 3:50 pm Post subject: phosphoric acid etch for windscreen installation?

Phosphoric acid is the basic ingredient in aluminum 'brighteners' that 

will surface etch the aluminum and make it the best it can be for 

bonding with paint and epoxies etc.  I use it to clean prior to alodine 

or painting.  I like to take an old terry cloth towel and soak it with 

the acid and wipe the aluminum down real good.  Flush with copious 

amounts of water, dry the surface and do the next step fairly quickly 

... whatever it is you're doing.



Linn

do not archive



Chris Johnston wrote:



 	  Quote: 	
		  hey all - 



what's the deal with this phosphoric acid etch stuff?  it says to do that before you install the windscreen fairing on page 45-18 step 9, but i have no idea what it means.  is there a special product you use to do this?  what the heck?



cj

phosphoric phool

do not archive

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Mon Sep 03, 2007 6:10 pm Post subject: phosphoric acid etch for windscreen installation?

Phosphoric acid etch is the first of two steps in alodine treatment of

aluminum Alclad.  The phosphoric acid is the etching process which

allows primer to adhere after alodine treats the surface.



If primer adheres better, then you might conclude that the adhesive

adheres better to retain the referenced part.



Ask Jesse about whether he followed that specific step and the method

used for replacement of the original windscreen after damage from errant

Columbia propellers.



John



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jwt(at)roadmapscoaching.c
Guest

Posted: Mon Sep 03, 2007 7:02 pm Post subject: phosphoric acid etch for windscreen installation?

Chris,



Spruce sells it as Alumiprep in gallon jugs. You dilute it about 2-1 with

water.  I used it as part of the Alodining and priming that I did to all

interior surfaces. I also am Alumipreping and Alodining all external

aluminum as part of the pain process. I apply the Alumiprep with a red

Scotchbrite and scuff it in real good. When the aluminum is almost a white

color it has worked well. Do not let it dry while applying and rinse it real

good. Some auto paint stores carry an equivalent aluminum cleaner (tried

some that did not work as well).



John Testement

jwt(at)roadmapscoaching.com

40321

Richmond, VA

Paint prep, interior, and LOTS of little stuff

do not archive

  



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ricksked(at)embarqmail.co
Guest

Posted: Mon Sep 03, 2007 7:51 pm Post subject: phosphoric acid etch for windscreen installation?

Good point John,



Should you alodine the aluminum after the etch just prior to installing the windshield?



Rick S.

40185

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CJohnston(at)popsound.com
Guest

Posted: Mon Sep 03, 2007 8:20 pm Post subject: phosphoric acid etch for windscreen installation?

hahahaha.  don't i feel foolish!  i've been Alumipreping and Alodining the whole way.  just didn't know I was "phosphoric acid etching".  hehe.  sheesh... it's hot out and my brain must've turned to mush.  thanks all!



cj

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jwt(at)roadmapscoaching.c
Guest

Posted: Tue Sep 04, 2007 4:02 am Post subject: phosphoric acid etch for windscreen installation?

Its so easy to brush some on for 5 min. Why not? I also used an Alodine pen

(from Stein) to do small areas. Its real convenient.



John 



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rvbuilder(at)sausen.net
Guest

Posted: Tue Sep 04, 2007 7:11 am Post subject: phosphoric acid etch for windscreen installation?

Alodine as soon as possible after etching or cleaning.  The Alodine process essentially is a controlled corrosion of the aluminum which creates a thin film barrier and then prevents any other corrosion from taking place.  If you wait you run the risk of filliform or other corrosion taking place first.



Michael



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rvbuilder(at)sausen.net
Guest

Posted: Tue Sep 04, 2007 7:14 am Post subject: phosphoric acid etch for windscreen installation?

I personally haven't done this but I don't see what the difference would be.  The common Lowes Depot products for "etching" and "cleaning" concrete prior to painting is nothing more than phosphoric acid.  Look for it in the paint section.  Just check the label and make sure it is straight phosphoric acid.  I believe the one Home Depot sells is even labeled as phosphoric acid.



Michael



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rene(at)felker.com
Guest

Posted: Tue Sep 04, 2007 7:30 am Post subject: phosphoric acid etch for windscreen installation?

Lowes sells the straight acid.  I found it in the floor tile department.  



Rene' Felker

N423CF

40322

801-721-6080

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AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Tue Sep 04, 2007 7:57 am Post subject: phosphoric acid etch for windscreen installation?

Grammatically speaking, Alodine does not "prevent" corrosion.  It does

however surely slow the process of benign neglect. 



The important points to the process are copious water rinse.  Use of

de-ionized water (not chlorinated or fluoridated.  No or very little

delay between phosphoric etch and final chromic "Alodine" final

hardening coat.  All metals want to return to a more natural state of

oxidation.



Alodine like Anodize do help create a harder and more resistant surface

coating.  Make it too hard and brittleness can cause a lack of some

desirable properties.



Good post Michael.



Johnny Horizon - KUAO



Do not Archive



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rvbuilder(at)sausen.net
Guest

Posted: Tue Sep 04, 2007 8:38 am Post subject: phosphoric acid etch for windscreen installation?

I do believe I said that it creates a barrier which helps prevent further corrosion.  



For anyone who has priced deionizing (DI) "kits" they tend to be a bit on the expensive side for no real good reason.  What I did was to go to my local Menards and pick up a couple of clear "whole house" water filters that were on sale for less than $20.  I then chained them together in series and put garden hose fittings on the in and out of the combined unit.  In the first filter I put a charcoal 1 micron filter to catch most of the garbage and iron in the water.  In the second I put a refillable DI cartridge that I picked up off of eBay.  The whole setup cost me maybe $60 and you can get bulk DI media off of various sites or eBay on the cheap.  If you are really anal you could add a third filter for water softening resin and a fourth for a cheaper throw away pre filter.  Just keep in mind that you will burn through a DI filter resin in a couple hundred gallons.



A well kept secret of car detailers is using DI water for a spot free rinse.



Michael



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John Ackerman

Joined: 19 Jun 2006
Posts: 130
Location: Prescott, AZ

Posted: Tue Sep 04, 2007 12:02 pm Post subject: phosphoric acid etch for windscreen installation?

Alumiprep is an etchant commonly used on aircraft prior to Alodining  

or painting; I suspect most of this thread is really about it or  

substitutes for it.



Alumiprep is a fairly dilute water solution that contains not only  

phosphoric acid, but also fluoride ion. That means that it contains  

HF (hydrofluoric acid). HF is very aggressive toward aluminum,  

dissolving the protective aluminum oxide coat from its surface. That  

exposes a fresh, uncontaminated aluminum metal surface to the acid  

solution. The aluminum then reacts very rapidly  with the solution to  

make hydrogen. You can see the tiny hydrogen bubbles forming on the  

surface. When the entire surface is making hydrogen and looks whitish  

from the layer of hyrdrogen bubbles, the Alumiprep has done its job.



The idea is that when you dissolve away the aluminum oxide coating,  

you also remove any contaminants (skin grease, paint, oil, whatever)  

that were on top of it, and have a fresh, active, reproducible  

surface to accept your alodine or whatever coating you may want to  

apply.



At this point you rinse thoroughly and dry, then put your chosen  

coating on as soon as you can.



A couple safety points:



1. HF is Godawful Nasty Stuff - it can eat away at you and not stop  

until it hits bone. Most chemists whom I know are truly respectful of  

it.  Phosphoric acid is also nasty, but nearly as bad.



2.  If you do like I did and put longerons and other long, narrow  

things into  a plastic pipe with Alumiprep, cap  the pipe, then rock  

and roll to cover the aluminum with Alumiprep, you WILL build up  

hydrogen gas under pressure in the pipe. There is a significant  

potential for pressurization of the pipe. There could also be a nasty  

explosion if a spark hit the hydrogen-air mixture you've made. The  

worst part of that is that the acid solution is something you really  

don't want on your skin, let alone in your eyes.

I vented the pipe frequently (several time a minute) to avoid  

building up pressure



On Sep 4, 2007, at 8:14 AM, RV Builder (Michael Sausen) wrote:



 	  Quote: 	
		   

 <rvbuilder(at)sausen.net>



 I personally haven't done this but I don't see what the difference  

 would be.  The common Lowes Depot products for "etching" and  

 "cleaning" concrete prior to painting is nothing more than  

 phosphoric acid.  Look for it in the paint section.  Just check the  

 label and make sure it is straight phosphoric acid.  I believe the  

 one Home Depot sells is even labeled as phosphoric acid.



 Michael

AV8ORJWC

Joined: 13 Jul 2006
Posts: 1149
Location: Aurora, Oregon "Home of VANS"

Posted: Tue Sep 04, 2007 6:05 pm Post subject: phosphoric acid etch for windscreen installation?

Outstanding safety advice.  All of it is accurate and timely.



John Cox



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