Statement of Purpose
Sapphire Metal Finishing believes in quality manufacturing at ALL levels. We want to build strong business relationships that provide long term benefits for our customers. We strive to help you succeed by providing excellent product finishes for your aluminum materials, pleasing your customers in turn. We supply consistent and attractive anodizing services with exceptional lead times.
At Sapphire Metal Finishing, we believe manufacturing is vital to our economy and community. We continue to invest in equipment, technology, knowledge, and skills to maintain our commitment to quality and excellence. We also welcome your feedback as we improve our services and processes.
We are committed to building a mutually beneficial partnership with each of our customers. In the following sections, we have compiled pertinent technical information regarding the anodizing process. This guide will help you understand and determine the specific anodizing services required by your business, and will aid you in ordering such services from Sapphire Metal Finishing. In some instances, adherence to these guidelines may help to reduce your anodizing costs.
If you have technical questions or would like us to provide anodizing tours or training to your team, please contact Sapphire at 208.614.4050.
Sapphire measures film thickness and surface dimensional changes using the mil, equal to 0.001 inch or 25.4 microns.
Anodizing Films Offered
Type II is often called decorative anodizing. We target a thickness of 0.6 mils on all of our Type II films as this thickness is more resistant to fading when dyed. 0.6 mils gives a durable finish and has a satin appearance. Many people prefer it to the more silver finish that a thinner film provides.
We have found that Type II clear on 2024 is much less attractive than on other alloys and most customers are happier with Type IIB clear finish for their alloy 2024 products when appearance is a factor.
Type IIB is a thin decorative finish. We target 0.25 mils for this process. If the product is dyed, then we recommend it be limited to indoor use. We recommend Type IIB for all 2024 clear finishes.
Type III is often called hard anodizing, although we have seen companies reference Type II as a hard finish, which creates confusion. Our Type III is a true hard finish.
We anodize the aluminum at a very low temperature and grow it to thicknesses of 0.5, 1.0, 1.5, and 2.0 mils. Because of the thickness and the density of this film, the clear color of Type III ranges from a bronze (6061) or silver-gold (7075) color for 1.0 mil to a dark chocolate (6061) or a dark gray (7075) color for 2.0 mils. The clear color is affected significantly by the aluminum alloy being anodized and the thickness of the film. All alloys dye black very nicely.
This film is primarily used when a very hard, abrasion resistant film is desired.
Color Consistency and Fading
Aluminum oxide is a relatively clear compound that cannot be dyed. However, anodizing film can be dyed as the process creates 4 billion pores per square inch of aluminum oxide, which are then packed with organic dyes, giving your product a colorful appearance.
Color consistency from batch to batch can be a challenge with anodized aluminum. Any factor that affects the pore dimensions and film thickness can affect the color of the finished product.
One such factor is the surface finish of the aluminum. Surface finish of aluminum is driven by the following:
- the aggressiveness of the final machining cut
- the sharpness of the cutting tools
- whether the surface is DA’ed or tumbled
- whether the part is lathed or cut in a mill
- raw material, both alloy and billet
The anodizing process also involves many variables affecting the pore dimensions. Pore dimensions variables include:
- the chemistry of anodizing tanks
- the amount of etch the product requires
- the electrical current density used to grow the film
- the dye concentrations and dye time
We strive to control the variables in our process to create consistent colors and are continuously making improvements to the controls. We also purchase high quality, single component dyes so that we maintain the highest levels of consistency.
We will work with you to determine the desired dye time for your products. If a dye time is not noted on the PO, we will dye your product to our standard saturation time for that dye.
The fade resistance of an anodizing dye is typically rated on a scale of 1-8, with 8 being the most resistant to fading.
To some extent, all anodizing dyes fade when exposed to UV light. In an effort to slow the rate of fading our dye tanks have high dye concentrations, our standard films are at recommended thickness for exterior exposure, and we purchase the most fade-resistant dyes in each color class.
The less dye concentrated in the pores of the anodizing film, the less fade resistant the film is. Therefore, we generally recommend leaving the product in the dye tank until it has reached full saturation.
Dye Colors Offered
The etch process creates a more uniform, matte appearance. Sapphire’s etch time options are zero, one, two, and three minutes. Unless stated otherwise, our default is a one minute etch. We are happy to provide samples to help you determine the etch time that meets your expectations.
Too long of an etch can highlight what we believe are grain structures in aluminum billet. These generally look like small ovals. We use a caustic solution in our etch process.
Etch process recommendations:
- Our standard process includes a one-minute etch. This tends to give the best, most consistent appearance on all alloys and for Type II, makes the final anodized surface nearly the same dimensions as the product before it was anodized.
- If you have a smooth, shiny, machined surface and want your final product to have the same appearance, do not etch the product.
- We strongly suggest alloy 2024 never be etched. Etching brings copper to the surface, which often creates color and quality issues.
- If your product is tumbled, then you should have it etched at least one minute.
- If you want a very matte finish and your product will receive a Type III film, then a two to three-minute etch time works well. (Three minutes on Type II often highlights the billet grain structures and is not recommended.)
- Forged 7075 should not get more than a 30 second etch. When 7075 is forged, a layer with high zinc concentration is created just below the surface. If, during processing, the anodized film extends down to this zinc-rich layer, it will be susceptible to delamination/flaking. It is best if it is not etched at all.
- Bead blasted 6061 should get a 2 to 3 minute etch. Bead blasted 7075 should get a 1 to 2 minute etch. The lower the etch time, the more seal smut will be visible on the bead-blasted product.
- There are contradictions in processing bead blasted 7075 (including forged). It is best not to etch 7075, yet to get a good black appearance on bead blasted 7075, it must be etched. Ultimately, we recommend etching occur because that has the larger impact on the appearance of the final product.
Our standard seal is a nickel acetate seal. We seal all products, unless the customer requests no seal. Nickel acetate helps close the pores created by the anodizing process, trapping dye and improving fade and chemical resistance. When a product has not been dyed, we can also provide a hot water seal, which is better for chemical resistance than the nickel acetate seal.
Omitting the sealing process should never be done on any dyed product or on products where discoloration from the adsorption of chemicals such as oil is undesirable.
Be aware that the seal process softens the surface of the anodizing film. The research lists values from a 3% to a 25% decrease in hardness when a product is sealed. Because of this softening, if the primary objective of anodizing is wear resistance, it is common for customers to request Type III unsealed. This will give the most wear-resistant layer.
Note: Some anodizing providers offer a Teflon coating on anodized films, stating that it improves lubricity. It does so only temporarily. The Teflon molecule is too large to adsorb into the pores and it will not chemically bond to aluminum oxide. Teflon coating is a thin layer that usually wears off fairly quickly. We have found no scientific, non-biased evidence supporting the use of Teflon coating on anodized films. Unless it is being used for mold release, Sapphire does not believe a Teflon coating is a good use of our customers’ money.
We offer bead blasting for those customers desiring a matte finish. We use glass bead so minimal material is removed from the surface. We are also able to mask off areas that are not to be bead blasted.
Masking and Plugging
We provide plugs, taped masking, and painted masking services for our customers.
Masking is used for three reasons, 1) to maintain an electrically conductive area for grounding or similar connections, 2) to prevent dimensional changes, or 3) to decrease acid bleaching or aluminum sulfate buildup in blind holes.
Our experience is that masking for dimensional reasons is specified much more often than it is needed. See “Design Parameters” for more information.
If your product receives our standard one-minute etch and a Type II film, then it should only be masked to prevent dimensional changes when tolerances are less than approximately 0.2 mils. This generally applies to some press-fit applications. We have run tests on threaded holes with no material effect on the hole. Variations on the etch time and the film type will impact your plugging choices as can be calculated using the information in the “Design Parameters” section.
For well controlled anodizing processes, the single biggest challenge is small, threaded, blind holes. These holes do not rinse well and can bleed acid during the dye process, creating bleached areas around the hole. This is also common on plugged large-threaded holes because the space behind the plug acts as a thermal pump; it sucks acid in through the thread during the cold processes and pushes it back out during the hot dye process. While we have not found a foolproof answer for the smaller threaded holes, we have found it is best not to plug larger threaded holes on dyed products.
We control our chemistry carefully, rinse carefully, and blow out all holes thoroughly to avoid aluminum sulfate buildup in blind holes.
Additional Notes About Aluminum Alloys as they Relate to Anodizing
We have extensive experience with 6061, 7075, MIC 6, 5052 and 2024. We have anodized other aluminum alloys, such as castings, 6063 and forged 7075.
- Forged 7075 can have delamination issues if not processed correctly. It is critical to tell us if the alloy is forged so we can minimize delamination risk.
- For the purpose of appearance, it is generally best not to etch or to minimize the etching of 7075 and MIC 6.
- Most alloys cannot be processed with other alloys, especially for Type III, as they rob current from each other during processing, causing non-uniform thicknesses and an increased risk of burn.
- Alloy 2024 must run at a much higher voltage than other alloys, requiring that it always be processed alone. It should normally only receive a Type IIB finish, especially with clear, for the best appearance and greatest color consistency.
- 6063 has a higher silicon content, which can cause a black haze on the surface of the anodized product. Typically, this haze is easily cleaned from the product.
For these reasons, it is very important that we know the alloy. Please note alloy types on purchase orders.
Maximum Dimensions of Parts Sapphire Can Anodize
Our tanks allow us to process parts in clear or black up to 99” long X 22” wide X 48” deep. Currently, we can process red, blue, orange and gold dye with the dimensions up to 12” long X 12” wide X 28” deep.
Product Dimensions and Design Information
Sapphire’s etch process removes approximately 0.25 mils per minute. The aluminum oxide film occupies roughly twice the volume of the aluminum that is oxidized to make the film; therefore, for every mil of aluminum consumed, the aluminum oxide film will be 2 mils thick. The net effect on the surface of the product is presented in the following table. The rows in blue show our default one-minute etch time.
Following you will find excerpts from the book “Aluminum – How To” by Robert H. Probert to illustrate concepts discussed in the above chart.
Hard Coat builds half into the surface and half on top of the original surface. Figure 8-2 illustrates how 0.002 inches thick looks on the diameter of a ¾ inch shaft. Half of the thickness is under the original dimension and half is on top. Therefore, 0.002 inches thickness (on two sides) of hard coat on an original 0.750 inch diameter shaft will now measure 0.752 on the micrometer.
The following excerpt and images summarize radius requirements in MIL-A-8625F and clearly explain the importance of these requirements for product design.
Normally the anodizing grows perpendicular to the surface. This has been confirmed by observing microsections. Figure 8-3 illustrates potential variations that can result from sharp corners on the part. Also, if the surface has been mechanically abused by blasting, sanding, tumbling, work hardening, etc. prior to anodizing, then the growth may be slightly different from perfectly perpendicular.
If the growth is perpendicular, an outside sharp 90-degree corner is left with a void. Similarly, in an inside corner the vertical growth crashes into the adjacent wall. The same thing happens on the inside of a round tube. When a certain thickness is reached, depending on the diameter of the tube, the growth crashes into itself and crazes or chips off.
Corners, therefore, should be rounded with the largest radius the part can stand and still be functional.
The Military Specification MIL-A-8625F, Table III, offer some recommendations for the radius of rounded corners for inside or outside.
If the coating thickness is: Radius of Curvature should be:
0.0001 inch 1/32 inch
0.002 inch 1/16 inch
0.003 inch 3/32 inch
0.004 inch 1/8 inch
Aluminum filler alloy 5356 should be used if a reasonable color match between the weld and the surrounding aluminum is desired. Most other filler alloys such as 4043 will leave a dark gray color and will not be attractive after anodizing.
It is important that the welds are cleaned thoroughly prior to oxidizing to improve the final appearance of the weld. Any areas that were overheated when welding will typically be visible through, and sometimes highlighted by, the anodizing film. The anodizing film grows differently and absorbs dye differently in the hot spot because the crystalline structure of the aluminum was changed in that area.
One should be aware that aluminum welds will not look as good as the surrounding metal. Minimizing hot spots, requesting that Sapphire only etch one minute or less, cleaning the welds well, and especially using 5356 as your filler alloy will give you the greatest chance of being satisfied with your final welded and anodized product.
Terms, Conditions & Ordering Information
New Customer Information
Thank you for the opportunity to earn you as a customer! In order to set you up in our system(s), we need the following:
- Completed Sapphire Customer Credit Application
- Your current ST-101, if applicable
The Ordering Process
Required PO Information
The Sapphire team wants to exceed your expectations! In order to ensure your product is processed correctly, it is critical that the following information is included with all orders.
- Requested film type and thickness
- Color and the dye time (when less than the standard saturation time)
- In the MIL spec, Class 1 is clear and Class 2 is dyed
- Etch time
- Aluminum alloy of the product
- Surface area
- We need the surface area to make sure we have enough electrical contact to avoid burning and have a uniform film growth. This can be pulled from your CAD properties.
- Plugging and masking requirements
- Special racking requirements (if applicable)
- Drawings of your product
- It is very helpful to mark masking requirements and special callouts on the drawing with a highlighter.
- Compliances required such as RoHS, REACH and ITAR
- Certification requirements
- We charge $6.50 for certifications and they should be a separate line item on your PO. We will bill it this way
- FFL requirements
If there is no callout, we use our standard process as noted in the Sapphire Anodizing Services Overview.
MIL-A-8625F Type II Class 2, Black
512 square inches
MIL-A-8625F Type III Class 1, Clear 2 mil
3 minute etch
102.4 square inches
Mask 3 holes per attached drawing
MIL-A-8625F Type II Class 2
Red 7 min.
2.3 square inches
MIL-A-8625F Type IIB Class 1, Clear
0 minute etch
62 square inches
Do not rack on exterior surface
Nickel acetate seal
MIL-A-8625F Type III Class 2, Black
0.5 min etch
84.6 square inches
Product requires an FFL
Upon receipt of your PO/Product, we will do a thorough review to ensure we understand what you want us to do. If we do not clearly understand your expectations, we will contact you for clarification. We will also verify that the quantity received matches the quantity on the PO.
We will notify you by email that your product is complete and ready for pickup/shipping. The email will be accompanied by the invoice. Please update us if company contact information changes.
All orders are FOB Sapphire Metal Finishing. At this time, you are responsible for product delivery and pick-up. We can ship via UPS/FedEx with Prepay and Add terms. If you wish us to ship on your UPS or FedEx account, please provide a return shipping label.
We will do our best to package your product the same way it was received or better.
Because we offer such short lead times, our standard credit terms are Net 15, with approved credit. If you would like different terms, please discuss with us in advance. Without approved credit, payment is due upon pick-up or prior to shipping.
We accept cash, check, ACH or Visa/Mastercard. Visa/Mastercard payments are subject to a 3.65% surcharge.
General Pricing and Lead Time
We strive to offer competitive pricing. If you ever feel our prices are not in-line with the market, please bring the issue to our attention so we can review with you and determine a fair and market-justified price given the value we provide.
We process orders grouped by type, substrate, etch, seal, and color. We can group the alloys by family. In other words, we can run all 6000 series alloys together, all 2000 series alloys together and all 7000 series alloys together. The 7000 series alloys include MIC-6.
Our standard lead time is four days for anodizing and five days for bead blasting and anodizing. If an order is extremely large, has significant plugging requirements, or requires us to order specialized racking or plugs the standard lead time may need to be longer.
Sometimes we receive small orders for less common alloys and thicknesses. These cannot be processed with the more common production runs. Our rectifiers are state of the art, but they must still have enough surface area to run at 4% or more of their rated capacity. On these occasions, we need to accumulate more product of the same finish specification to complete the order.
We will do what we can to accommodate special lead time needs.
Anodizing Risks – When Things Go Wrong
Even with extensive care and precaution, there are occasions when anodizing goes wrong. Anodizing is a very complex process with many variables. Because of this, there is risk associated with the process. We recognize anodizing is the last step in the long, and often expensive, process of creating a finished product. We do all we can to mitigate the risks and implement permanent, process-oriented corrective actions when something does go wrong. See a summary of possible risks below.
- We run very high turbulence in our tanks. This helps us to achieve high quality, consistency, uniformity and a lack of contamination critical to an excellent anodizing finish. The downside to this is that parts occasionally wash off in our tanks. We do all we can to find them, but the reality is that parts can go missing.
- There is a lot of human handling associated with racking, un-racking and blowing off parts. Occasionally, parts will be dropped. The parts usually land on the rubber mats we have in place and are undamaged. However, they can hit each other or the concrete and thus incur damage.
- A part may burn if we do not have adequate electrical contact. This doesn’t happen when we have an accurate surface area figure, but there is risk when we have to estimate/calculate the surface area. Please be sure you’re providing your surface area numbers. Refer to Required PO Information.
- With new finishes, new products and complex racking situations, the probability of things going wrong increases.
We are not responsible for replacing or compensating for any parts lost or damaged. When process failures do occur, Sapphire will institute corrective actions to prevent the problem in the future. Corrective action reports are available at the customer’s request.
We guarantee our services. If you are not satisfied, we will reimburse the monies you paid to Sapphire for processing the specific part(s). Alternatively, when possible and with your input and agreement, we may rework your parts at no charge. We do not warrant for any additional costs, damages, legal fees, losses or issues beyond what you paid to Sapphire for the specific services requested.
We welcome all feedback and use it to improve our procedures, prices and services.