MIL-PRF-8625F · Type II and Type III · Run On Site
Aluminum Anodizing to MIL-PRF-8625F, In House
120-inch tanks, sized to match our largest cutting envelope. Anodizing changes more than the color of a part. It changes the size, the corrosion resistance and, on hardcoat, the wear resistance. We machine and anodize the same part, so both halves of that change are ours to own.
Tank Length
120 IN
Matches our largest machining envelope
Process
MIL-PRF-8625F
Sulfuric acid anodizing, run on site
Colors
Black, Clear, Red, Green, Blue
Custom on volume
Aluminum Only
120 Inch Envelope
Anodized On Site
Masked And Marked
Will it fit
Section 02 / 09
How big a part can you anodize?
120 IN
Largest Tank Length
The length of our largest tank
That is the length of our largest tank, and it is not a coincidence that it matches the 120 inches of X travel on our largest machining center. We sized the tanks to match the machine on purpose. If we can cut it, we can anodize it.
There is always someone with a bigger tank somewhere, and always someone with a bigger mill. For the range of parts this shop actually builds, running the finish under the same roof as the cut has mattered more than chasing a bigger number. So the honest answer past 120 inches is no, not maybe, and you will hear that on the phone before your print sits in a queue for a week.
One thing worth saying now, because it comes up later on this page: fitting in the tank and coming out at the right size are two different questions. The second one is where most anodizing surprises happen, and it is section 4.
Colors and the honest gaps
Section 03 / 09
What we run today
Five standard colors, and the two anodize types that cover almost everything an aluminum part needs. Clear means undyed rather than colorless, so a clear hardcoat comes out gray on 6061 and closer to gold on 7075.
Clear
Type II or Type III, Class 1
Black
Type II or Type III, Class 2
Red
Type II, Class 2
Green
Type II, Class 2
Blue
Type II, Class 2
Hardcoat
Type III, Class 1
Already have a print and a target date?
What it does to your part
Section 04 / 09
01
What actually happens to your part
01
Clean and Etch
Oils and the natural oxide come off first, so the tank has bare aluminum to work with, not whatever was on the part when it arrived.
02
Anodize
Direct current in a sulfuric acid bath grows a porous oxide layer up out of the aluminum itself. It is not a coating applied on top. It is the top of the part, converted.
03
Color
If it is not staying clear, dye soaks into the open pores of that oxide layer before they close.
04
Seal
Hot water or a chemical seal closes the pores, locking in the color and most of the corrosion resistance.
05
Mask and Mark
The same floor blocks color from a bore or a mating surface, and laser marks a logo or part number into the finish once it is done.
02
What anodizing actually does to your part
- It becomes part of the metal, not a layer on it Paint chips, flakes and scratches down to bare metal. Anodize cannot flake off, because there is nothing separate to flake. What corrodes on an anodized part is the oxide itself, which is the reason it resists salt spray and handling far better than a painted or plated surface does.
- Hardcoat buys wear resistance, and it is not free Type III runs thicker and harder than standard anodize, which is why it goes on wear surfaces and sliding fits. That same thickness is why hardcoat needs a bigger edge radius than the part might have been designed with, and why a hardcoated part is more likely to chip at a sharp corner than a Type II part is.
- The part gets a little bigger Roughly half the coating grows out of the surface and half grows into it, on every anodized face. A bore closes. A shaft grows. A threaded hole moves more than either. None of that is a defect. It only becomes a problem on a print nobody told us needed to survive it.
- Color you can count on, mostly Sealed color does not fade the way an exposed coating does. Shade is another matter. Dyed color lands in a range around the target, and two parts from the same tank can come out slightly different. Holding the chemistry in line keeps that range tight. If a part needs an exact match, tell us before it runs and we will agree on it in writing.
Whose parts, and questions
Section 05 / 09
More than half of what we finish, we did not machine
Shops send us parts to anodize that they cut themselves, including shops that machine the same kind of aluminum parts we do. That is most of this line's work in a given week, not a side business.
We take the part as it arrives. We do not requote your machining, and we do not tell you how we would have cut it. What we will tell you, before it goes in the tank, is anything on the print that anodizing is going to change, because that conversation is cheaper before the part is coated than after.
Questions we get before a part ships to us
Will anodizing throw off a tight tolerance?
It changes the size in a predictable way, and predictable is not the same as invisible. If we know a feature has to hold a tight number after anodize, we account for it before we cut. If we find out after the print already crossed our desk as “finish only,” that is where problems start. Tell us early and it is a design input. Tell us late and it is a rework conversation.
Why did my black parts come back with a purple tint?
Almost always a seal issue, either the seal chemistry or the timing after dyeing, not the anodize itself. It is one of the most common complaints in this industry and one of the easiest to prevent with a controlled process. Send us a part that has done this before and we will tell you what we see.
Our drawing still says MIL-A-8625. Is that a problem?
No. MIL-PRF-8625F superseded MIL-A-8625, and many drawings still carry the older number. If your contract calls for a specific revision, tell us when you send the print.
The Straight Answer
Will anodizing wreck my tight tolerance?
Only if we do not know it is coming. Growth from anodizing is predictable, and a machinist who knows a feature is headed for the tank plans for it the same way we plan for anything else on the print. What we cannot do is guarantee a number on a feature we were never told had to survive a finish.
That is the actual argument for one roof. It is not that we are nicer to deal with than a shop that ships parts out for coating. It is that the same person who can adjust a tolerance for anodize is standing at the same machine that cut it.
Proof
Section 07 / 09
Over half of this line's work walks in from another shop's floor
Most weeks, more than half of what goes through our tanks was machined somewhere else. Some of those shops cut the same kind of aluminum parts we do. They send us the finishing because the finishing is what we built, on purpose, at a scale most machine shops never bother to.
One customer put it in writing after four years of buying from us:
“A proven supplier of machined components, assemblies, and engineering services provider for the last 4 years… their anodizing line has proven to be cost effective and schedule compliant on 3 Day Quick Turns.”
JR Automation
Before you ship
Section 08 / 09
What to send with the part
Quantity, and whether this repeats.
Alloy and temper, if the print does not already call it out.
Color, and whether it has to match hardware you already have in the field.
Any feature that has to hold a tight number after anodize. This is the one buyers forget and the one that causes the most rework.
Masking or laser marking requirements, and where.
Target date, and whether it is real or padded.
Any ITAR or export-control flag on the part.
Surface condition. Anodizing will not hide machining marks, scratches or staining, and it can make them easier to see.
Send that much and we can tell you, before the part is in the tank, whether anything on the print needs a conversation first.
The Ask
Send us the part.
Tell us what has to survive the finish and we will tell you what changes. Everything else is the easy part.
