etch....desmut.....deoxidize.........weeeeeeeeeeeeeee

[Sid03]

Im currently using the following prep steps....

* SP cleaner @ 140degrees- varied times
* Desmut/deoxidizer @ 110degrees- 1 minute

What im wondering is should I add an etch step, or should the caswells desmut/deoxidizer take care of any oxide buildup on the aluminum(in the case the parts have sat around awhile after polishing/bead blasting)?

Thanks

[Sid03]

oh somebody has to know this......................??

[sswee]

From my experiences and reading posts. I add an etch step before the DeOx-DeSmut when dealing with cast or unknown grades of aluminum. On the cast parts especially, the parts smut up in the etch step. Then the DeOx-DeSmut Takes it off before anodize. The only problem I've seen is if the parts are highly polished, it takes some of the shine out of them depending on time in the etch. I am using Sodium Hydroxide for my etch.

[Sid03]

so if parts are freshly machined, or have only been sitting around 1-2 weeks MAX after stripping and prepping......would the etch step be needed, or would the desmut/deoxidizer be enough?

I mean......deoxidizer.....isnt that what the etch step would in turn be doing also?

[sswee]

According to my experience and everything I have read, on a freshly machined part or one that was prepped recently, the DeOx/DeSmut is all that is needed. The DeOx/DeSmut takes off any natural oxides grown from the part just sitting around. I add the extra etch step (sodium hydroxide) only on cast aluminum parts because of smut problems caused by impurities in the cast. I have seen posts saying the DeOx/DeSmut will take care of this problem without the extra etch step but haven't had time to test it. The automotive cast parts I've run into seem to be made of really trashy material. If you are dealing with known grade aluminum and especially fresh machined, you should only need to prep, degrease, DeOx/DeSmut, and anodize.

Sorry for going on a tangent.

so if parts are freshly machined, or have only been sitting around 1-2 weeks MAX after stripping and prepping......would the etch step be needed, (NO) or would the desmut/deoxidizer be enough? (YES)

A question for you. From previous post dates and conversations with Fibergeek that you have had, would you be yankin my chain as they say?[/b]

[Sid03]

nope, not yankin any chains

In the 2 instruction manuals I have, and the reading I have done, I have found very little mention of the etch step in any kind of detail. From what im told it is for, i would think the deoxidizer step does the SAME thing......

im simply debating adding it to my process, and still know very little about etch in general. Fibergeek spoke as if I needed it in any case scenerio.........if thats the case, im very curious as to why caswell didnt include it in their kit.

[sswee]

The DeOx/DeSmut is an etch step. It is not as aggressive as some other chemicals. Aluminum that has setup for months oxidizes enough to turn the color from a bright silver to a dull gray. At this stage it takes something aggressive to remove it, ie. machining, sanding, blasting. I bead blast my parts in that case. If I machine parts and cannot get to them for a little while, I'll spray them with WD-40 to retard oxidation. Are you having a problem to cause you to consider the need for an extra step? Sifting through old posts can get confusing, as some were written before and in the beginning of LCD. I only have one book, so I do not have anything to compare to. I have seen descrepancies that appear to be from documentation not keeping up with procedure. The only thing I can think of without seeing would be the anodize stripper that is used to strip a part that has been anodized and needs to be stripped to be reanodized. The DeOx/DeSmut comes in the kit, at least it does now. I don't know if it always has.

[Sid03]

would a short time in stripper be equal to the etch step?

[sswee]

I plan on getting some stripper, but don't have any yet. The stripper is Potassium flouride. It is suppose to strip the anodize without eating the aluminum. On the other hand, the DeOx/DeSmut is a mix of sulfuric and I think phosphoric acid designed to clean contaminates, ie: copper, oxides. According to pg.115 of my book, the etch step with anodize stripper can be skipped. They warn the stripper will take the shine out. The two processes are not the same. The effect on the material is a major indicator. Are you having a problem to cause you to consider the need for an extra step? (high resistance during anodize, not thick enough coating, poor dyeing)