From Laurie Trembly, Human Resources Manager
Ask Jack: Mixed Alloys
The Colour Changing Card Trick
See below video and find out your multi-task capability in particular observation. How many changes did you spot???
Micralox Goes to World Congress on Aluminium, Bologna, Italy in 2011
Title: MICRO-CRYSTALLINE ANODIC COATINGS – A REVOLUTIONARY PLATFORM TECHNOLOGY IN CORROSION PROTECTION
Tim Cabot, Jack Tetrault and Mike Sung
Presenter: Jack Tetrault, Sanford Process Corporation; COO Duralectra-CHN, LLC
Summary
A basic requirement for finishing aluminum is to protect the volatile untreated surface from corrosion attack. However, current solutions provide insufficient protection and therefore limit the areas where aluminum can be used or require more expensive solutions such as polymeric overcoats.
The advent of a new technology that retained many of the design, process economics, and engineering characteristics of anodic coatings while fundamentally changing corrosion resistance would solve many existing problems and open broad new uses for aluminum.
In 2010, the parent company of The Sanford Process Corporation, Duralectra-CHN issued a set of patents on Micro-Crystalline Anodic Coatings where conventional amorphous oxide created by Type II/Type III anodizing was converted into closely knit micro-crystalline structures. Phase changing a portion of the oxide in this way creates an effective barrier to corrosion attack by dramatically lowering the rate of chemically induced solubility of the oxide (for instance in the presence of high/low pH chemistry, galvanic conditions, etc.) while lowering overall surface to substrate activity. Further, the novel coating protects entrapped dye colorants in the pores from superheated steam allowing articles to be sterilized and/or cleaned in dishwashers without fading and discoloration.
The paper provided for this conference will examine this new oxide, how it is constituted, and the performance results in various application studies vs. conventional anodic coatings.
2010 D-CHN Quality Audits
D-CHN has been ISO 9001:2008 certified since 2007. Since then we have invested generous amounts of time and effort to improve our quality system. Many of our customers and potential customers, under increasing pressure to find finishers with certified quality systems, decided to audit us to investigate our system in terms of documentation and floor practice. Due to these factors, 2010 was one of our busiest years for customer audits. More than 10 key business customers and our primary ISO auditor, Perry Johnson Registrars visited D-CHN to examine our quality system and compliance status. These customers include those involved with manufacture Class II medical devices and who are ISO 13485 certified. Below are some of their site audit comments which give strong testimonials to the improvements we have made over the previous years.
Perry Johnson Registrars
“Notable process improvements on the production floor.”
“QC inspector is less stressed and everyone is more confident in what they are doing”
S* & N*
“I am blown away on the mach improvements in the Quality systems since the last audit in 2007.”
“Everyone I met was helpful and knowledgeable. The Facility appears well organized. I feel that the management team has demonstrated a firm commitment to quality and continuous improvement.”
I*D*
“ In all my years of conducting site audits, I have never not issued a major, and no minor findings.”
“I was very impressed by your QMS, and am very much looking forward to working with you more into the far future. Thank you so much for allowing me to visit. Duralectra-CHN was one of the funnest companies that I have visited in a very, very long time.”
St**
“We are impressed with your Quality systems, D-CHN surpasses all anodizers that I have worked with in the past 20+ years.”
E** Aerospace
“D-CHN is the only anodizer ever that did-it-right the first time.”
GERMANY & BEYOND
D-CHN and our sister company Precision Coating Company (www.precisioncoating.com) set off for Dusseldorf, Germany in November to take part in the MEDICA show. Up to this year, attending this huge gathering of the global medical products companies seemed – well, beyond us and too big a stretch.
With the launch of MICRALOX, a patented, micro-crystalline aluminum oxide that revolutionizes corrosion and steam resistance, we had a story this year that easily translated into all the languages spoken at MEDICA. In part, this is due to the fact that concerns about prion diseases in Europe haves caused a general trend is to use higher pH, and thus more severe, detergents to clean reusable medical equipment. Conventional anodizing and hard coat does not perform up to expectations in these conditions, however, people want to use aluminum for all of its excellent properties. The MICRALOX message was well received. Consequently, preliminary discussions to license the technology into the European market have started. MEDICA was the first international show – now the schedule will take us, and MICRALOX, even further beyond.
Anodizing Issues with Aluminum Castings
A recent correspondence from a customer inquired about difficulties that they were having with the hard anodizing of a cast product. The product was receiving a black hard coat anodized coating and they were experiencing several problems with all the vendors they had chosen.
First, the product needed to be a very dark black color with no un-anodized spots or spots of discoloration. Second, the product had to be capable of passing salt spray specifications for hard coat anodize that are normally expected of wrought alloys; and lastly, the product had to be processed economically.
After reviewing the criteria and possible solutions D-CHN along with its sister company Sanford Process Corp., was able to engineer a process that enabled the customer to meet his requirements without costly additional steps like impregnation. Sanford “Plus” along with some “magic powder” solved the issue.
“The Sanford Plus Process and the “secret ingredient” enabled us to create an oxide film of nearly flawless character” said a D-CHN technical advisor. This coating offered the perfect solution to the deep black color and the salt spray resistant requirements demanded by the end user and, because it was only a few added steps, the added cost was kept to a minimum.
The problems that were causing our customer missed deliveries, sub-par quality and significant lost dollars in returns and wasted time were eliminated by the D-CHN and Sanford technical staff.
When it comes to castings, we have the “solutions”.
Electrolytic Coloring of Hard Anodized Aluminum Alloys
By Leonid Lerner
INTRODUCTION
The electrolytic coloring (“two-step”) process was first in use in Europe and Asia during the 1960’s (Asada Process), and was introduced in the USA during the 1970’s by ALCAN. The earliest claim to coloring anodized aluminum belongs to Italian scientist Dr. V. Caboni. Dr. Caboni received an Italian patent in 1936 for impregnating aluminum oxide film with finely divided metal from aqueous solutions of the salts of copper, nickel, silver or metals electropositive to aluminum. The final product of the two-step process is conventional anodized (soft) oxide film with coloring done in a subsequent step, as shown in Fig.1. The coloring is produced by electrochemical action using a proprietary second step electrolyte, which contains the dissolved metal salts of tin, cobalt, nickel or others.
Alternate Current (AC) power is applied to the process tank by means of a counter–electrode. The applied AC power deposits metallic particles (pigment) of salt in the pores of the “first step” aluminum oxide film. The color is developed as a result of the optical effect produced by light scattering of metals, which have been deposited in the pores of oxide film. The electrolytically colored oxide film demonstrates very good weathering and corrosion resistance vs. colored oxide film formed by immersion in organic dye or in an inorganic metal salt. The differences between immersion in organic/inorganic dye and electrolytic coloring are:
- In Immersion, the absorption of dye/salts occurs on the top portion of the pores while in two-step coloring metallic colloids deposit at the base of pores. (See Fig.2)
- The organic dye may fade or discolor under sunlight while electrolytic coloring has excellent light resistance to fading caused by light.
- The organic/inorganic dye will remove if the oxide film partially wears out vs. electrolytic coloring. (See Photos ##1, 2 & 3).
BACKGROUND OF STUDY
According to the recommendations of the Aluminum Association1, the preferred aluminum alloys for “two-step” coloring are AA1XXX, AA3XXX, and AA5XXX & AA6XXX. The aluminum alloys of 2XXX, 7XXX series and casting are not recommended for electro coloring because of poor results.
The purpose of our study was:
- To find whether the low voltage DC+AC Power Supply2, used as the first step procedure in “two-step” electrolytic coloring, would demonstrate better results in color acceptance and hardness on different series of aluminum alloys, especially 2XXX and 7XXX series.
- To compare the TaberTM abrasion resistance test between the two processes.
- To determine the maximum time break between first and second step in the “two-step” coloring process and compare between the two processes.
In our studies we employed 2 different power supplies. For conventional anodizing as first step we used a DC Power Supply (0-15 VDC) and a DC+AC Power Supply2 (0-12VDC). (See Fig.1 & Fig.3) All samples were 4”x 4” squares (32 sq. in) of 2024-T3, 6061-T6 & 7075-T6 aluminum alloys. Prior to this study some “first step” anodized samples, including 2024-T6, were sent to Clariant laboratory for electrolytic coloring. The time break between the “first step” (DC+AC anodizing) and “second step” (electrolytic coloring) was approximately 72 hours. All samples show a good color acceptance. (See Tables 4 & Photos ##6, 7, & 9)
The electrolytic coloring as “second step” was done using an AC power supply (60 Hz) with a maximum constant voltage of 20VAC. The counter–electrode in the plastic process tank was made from stainless steel. The bus bar was made from aluminum 6061-T6. A filtration pump in conjunction with a 10-micron filter was installed. The pre-mix electrolyte was SandocolorTM supplied by Clariant Corporation. In most cases the coloring cycle was 10 minutes. All samples were sealed for 5 minutes in (185ºF) Nickel Acetate solution.
TABLES
Table 1 displays the different data related to the first step anodizing with the same electrolytic coloring techniques for all samples in the experiment.
- Column#1 is the name of the process and identifies the part number of each sample. The power supplies used were a conventional DC Voltage and a proprietary Low Voltage DC + AC
- Column #2 contains the electrolyte composition.
- Column #3 contains the electrolyte concentration in grams per liter.
- Column #4 contains the temperature of electrolyte in º C during the process.
- Column #5 contains the temperature of electrolyte in º F during the process.
- Column #6 shows the time of the hard coating process in Minutes.
- Column #7 shows the maximum voltage used in the process.
- Column #8 shows the maximum current density (Amps/sq. ft.) reached during the process.
- Column #9 shows the thickness of the coating in mils, determined by averaging at least nine measurements from different spots on the samples.
- Column #10 contains the type of aluminum alloy.
RESULTS AND ANALYSIS
Electrolytic Dyeability
Our study of samples in Photo # 11 shows:
- Different intensity of dark color on 6061-T6 electrolytic colored aluminum alloys between Conventional DC anodizing sample (CA-2) and DC+AC hard anodizing sample (2S#9)
- The DC+AC process visually demonstrates deep dark and uniform appearance of color.
Time Break Between First and Second step in “two-step” Electrolytic Coloring Processes
72 hours after the different anodizing processes (DC and DC+AC), the samples (2024-T3, 6061-T6 & 7075-T6 aluminum alloy) were electrolytically colored during 10minutes. The samples run by DC+AC process demonstrate very promising results on absorption and uniformity of color after spending long hours in the open air as compared to the conventional DC process, which showed the different intensity, uniformity and poor dyeability. (See Photos #4 & 5).
Taber Abrasion Tests
Mil-A-8625F specifies that the anodic coating shall have a maximum wear index of 3.5 mg/1000 cycles (or 35 milligrams of weight loss per 10 thousand cycles on aluminum alloys having a copper content of 2 percent or higher) and 1.5 mg/1000 cycles (or 15 milligrams of weight loss per 10 thousand cycles on other aluminum alloys). We cannot compare the abrasion resistance of oxide films after electrolytic coloring to Military Specification numbers, but we try to compare results between the two processes (DC & DC+AC).
Our study of Tables 2 & 3 shows:
- The abrasion results produced on 2024-T3, 6061-T6 & 7075-T6 aluminum alloys after the DC+AC “first step” process surpassed the results of the Conventional Anodizing DC process.
- The Wear Index results of coatings produced in DC+AC anodizing process exceed coatings produced by Conventional DC process.
Bibliography:
- 1993 PF Directory “Anodizing Aluminum” by J.G. Hecker, Jr.
- 1972 Surface “Treatment and Finishing of Aluminum” by S.Wernick & R.Pinner
MICRALOX Accelerated Corrosion Testing Update: (1) 336 Hours of Salt Spray Test per Mil-A-8625F
MICRALOX has been tested salt spray corrosion resistance per Mil-A-8625 F. Per Mil-A-8625F, test specimens, prepared using 3 by 10 inches panels having thickness of 0.063 inches, subjected to a 5 percent salt spray test in accordance with ASTM B 117. After exposure of 336 hours, specimen is visually examined to determined that all of the following conditions are met:
- Test specimens shall show no more than a total of 15 isolated pits, none larger than 0.031 inch in diameter, in a total of 150 square inches of test area grouped from five or more test pieces.
- Test specimens shall show no more than 5 isolated pits, none larger than 0.031 inch in diameter, in a total of 30 square inches from one of more test pieces.
We are pleased to announce that MICRALOX passed 3,048 salt spray corrosion resistance hours as of October 5th. It will be continuously going as long as we get a good result. The report is attached for your information. Stay tuned for further results.
