I'm thinking of having a lower refinished in Duracoat, but I'm hesitant to rough up & partially remove the existing anodizing. I just want to refinish it for aesthetic purposes (change the color from light grey to flat black), so I was wondering... can I just degrease & refinish or do I really need to prep the surface any further?

Thanks.  

Just degrease and refinish.  Don't blast off the hard anodizing still on your rifle.

I've done gray lowers black, black lowers OD, made unmatched uppers and lowers match, all with Norrell's Moly Resin.

Quoted: Just degrease and refinish.  Don't blast off the hard anodizing still on your rifle. I've done gray lowers black, black lowers OD, made unmatched uppers and lowers match, all with Norrell's Moly Resin.

That's what I'm thinking, but while talking to the compny that I was going to send my lower to (I'm not doing the refinishing myself) I was told that their SOP is to "rough up" the surface with a light oxide blast so that the finish will adhere better.

Will Duracoat adhere properly to just a degreased hard anodized finish?  

if you turn down the blast pressure to around 40PSI you should be able to safely remove the finish without touching the anodized layer.

It's not that easy to remove the anodized layer.

That said, it's not necessary since most AR anodized surfaces already provides a nice, rough surface that helps molyresin adhereance.

The only time I would blast is if you got one of those DPMS teflon coated receivers, which the moly resin will not adhere well to.

Quoted: Harcoat anodizing is the coloration process, it's not like they anodize it then put color on top.

That's not quite right.  Anodizing itself has nothing to do with the color.  It's a process that converts the surface of the alloy metal into a hard coat with microscopic, honey cone shaped patterns.

the colorization is only done afterwards using special dye, which is held by the honey cones, and then sealed.

Factory anodizing is fairly thick and it isn't something you can easily remove by blasting.  Otherwise why would refinishers need to "chemically" strip anodizing, when all they need is blast it?

Duracoat is a top coating, a paint.  Anodizing is a conversion finish similar to parkerizing on steel.  The industry standard is to apply paint type top coatings on top of a conversion finish.  This is optimum for both adhesion and corrosion resistance.  Some examples of small arms manufactures that do/did apply a top coat over a conversion finish include:

FN
Izhmash
Tula
BSA
FMAP
Imbel
Bulgarian Arsenal
FEG
Enfield
Beretta
SW&H
IMI
Lithgow
etc, etc

Can't think of one small arms manufacturer that paints right on top of bare metal.  Maybe Century or Vulcan arms would?

Darkest2000 made a good point, some manufacturers apply Teflon, and not much of anything sticks to that stuff.

For more information specifically about Duracoat paint read gunplumber's post here:

www.falfiles.com/forums/showthread.php?s=&threadid=105072

I think some posters are getting confused about anodization. Hard anodize is the surface conversion process(hardens the surface). Anodization(in this case) is a secondary coloring process.

There is also a difference in a light blast, and blasting until it's back in the white.

I don't think blasting is necessary, but it can't hurt as long as it isn't overdone.

Quoted: Quoted: Harcoat anodizing is the coloration process, it's not like they anodize it then put color on top. That's not quite right.  Anodizing itself has nothing to do with the color.  It's a process that converts the surface of the alloy metal into a hard coat with microscopic, honey cone shaped patterns. the colorization is only done afterwards using special dye, which is held by the honey cones, and then sealed. Factory anodizing is fairly thick and it isn't something you can easily remove by blasting.  Otherwise why would refinishers need to "chemically" strip anodizing, when all they need is blast it?

Actually you are both right in some respects. Type-III anodizing will color the aluminum, anything from Gray to Black, depending on the thickness of the coating and the chemicals added to the anodizing tank, however it is expensive, time consuming, difficult to control and many of the chemicals used are very hazardous and poisonous. Type-III is difficult to dye due to the small pore size of the coating, so in most cases it is not even attempted. The problem is, that in most cases, the term Hard-coat no longer means that it is Type-III anodizing. The specifications for Type-III are very strict and the only method of confirming that the anodizing is in fact Type-III is either by using an electron-microscope, or by destructively testing a completed piece by chemically removing the anodic coating, titrating it, drying it, and weighing the results to determine the number of cells per square inch. Rather expensive and usually only done in scientific and military applications.

Type-II anodizing is dyed and the dye is absorbed into the cells of the coating. Basically the only requirement is the thickness, and that there be enough cells created to hold the color dye and give a uniform appearance.

In either case, if it is blasted and the color is removed, so is the anodic layer. Think about it. In Type-III, since the color is from the thickness or chemical composition of the cells themselves, removing the color removes the cells. In Type-II, if the cells hold the color, and the color is removed, then so are the cell walls.

Why chemical removal is used, is it is easier, more precise, and if done properly is less destructive to the base aluminum. Other reasons: (1) You can dunk 100 pieces into a tank and have them all stripped in 10 minutes. Much easier and cost effective than having someone blast each piece individually. (2) It is also easier to control the amount of material removed, since the stripping action proceeds at a specified rate. Controlling the amount of material removal, when dealing with thicknesses of 0.001" is almost impossible when blasting, increasing the potential of base metal removal. (3) Blasting also tends to excessively change the hole dimensions more than chemical stripping does. (4) Getting into small nooks & crannies is difficult with blasting. With chemical removal its not an issue as long as the remover can reach it. There are even stripping chemicals available that only remove the aluminum oxide coating and don't harm the raw aluminum underneath.

As for thickness, its all relative. Thickness spec's for Type-II are a coating LESS THAN 1mil (0.001"), while Type-III is anything OVER 1mil.

Although most AR-15 manufacturers state that they are hard-coated, they are just a thick Type-II coating, usually 1.1-1.2mils thick. The term hard-coat has come to mean different things to different people. Hard-coat, at one time, was just another term for Type-III. (Type-III specs require a specific process, with  a coating thickness in excess of 1mil, that was also of a specific density of cells per sq. in). It no longer means this. Most manufacturers use this term to mean that it is a Type-II coating slightly thicker than 1mil. The cell density requirements are ignored.

How to tell the difference? You can't, and the manufacturers know it. Unless they say specifically that it is a Type-III coating, it all means nothing.

Now, on to NYPatriot's question. If you are going to Duracoat it yourself, do nothing but clean and degrease. The anodized coating makes a good base and requires no additional prep work. The anodized coating, microscopically, is very rough, so the bond should be good if the Duracoat is applied with multiple, VERY thin coats. I've used Norrell's Moly Resin and an airbrush and have gotten superb results with no adhesion problems. Based on others who have used it, I assume that Duracoat will perform the same. Actually it is the best of all worlds to Duracoat or Moly OVER an existing anodized coating. The anodizing adds the surface hardness and corrosion resistance to the raw aluminum, while the Duracoat adds an additional layer of corrosion protection above this (as well as providing an easy to apply appearance).  Moly Resin also adds lubricity to the coating, which aids in reducing wear. I'm not sure if Duracoat does this but from what I've heard it is an excellent product.

Quoted: Clueless.

well, same can be said about you

And try to quote properly.

allright kids,if you are done ,do what lauer does before they duracoat a part ,they manganese phosphate the part parkerise solution


you gotta quit actin like that nothing positive gets accomplished.everyone hates a knowitall and most people don't know it all so mistakes can be made.I don't know it all and this may not be what you need.

Simple answer: Don't blast , just paint the way you like.  Use acetone to clean.

Quoted: Clueless.

Well, I wouldn't have been that harsh. Technically, it's an easy subject, however, it has gotten more confusing over the past few years. This is mostly due to mis-use of terminology used by 'marketing types' to hype their product. Then when you add in the multiple types of anodization processes its easy to understand how the confusion develops.


Want to really confuse people, add in mil-spec anodizing to the discussion.

But, back to NYPatriot's rpost (instigator that he is ), just simple green it, rinse, spray or dunk in acetone (if you think it needs it) and Duracoat it. This thread is already longer than it will take you to paint your lower.