Anodized aluminum corrosion test

ASTM Standard B 538-70, Method of FACT (Ford Anodized Aluminum Corrosion Test) (Withdrawn 1987). 

The CASS test and Corrodkote procedure are employed primarily for testing decorative chromium systems, with the CASS test ako being useful for testing anodized aluminum. These tests were developed to give a more rapid indication of corrosion resistance and a better correlation with service performance. They have come into prominence tis the most widely used modifications of the salt spray test because of their greater speed. Both tests employ cupric ion in the corrodant... 

F.F. Booth and H.P. Godard, An Anodic Stress-Corrosion Test for Aluminum-Magnesium Albys, First International Congress on Metallic Corrosion, Butterworths, 1962, p 703-712... 

Vanadium is resistant to attack by hydrochloric or dilute sulfuric acid and to alkali solutions. It is also quite resistant to corrosion by seawater but is reactive toward nitric, hydrofluoric, or concentrated sulfuric acids. Galvanic corrosion tests mn in simulated seawater indicate that vanadium is anodic with respect to stainless steel and copper but cathodic to aluminum and magnesium. Vanadium exhibits corrosion resistance to Hquid metals, eg, bismuth and low oxygen sodium. 

The combination of acid precipitation with road salt spray produced the worst effects on anodized aluminum. As the MIST test pH became more acidic and the amount of salt increased the time to achieve an equivalent milky white appearance was reduced significantly (Table I). At more neutral high chloride concentrations severe pitting occurred while at more acid high chloride concentrations blush and bloom predominated. The latter environment is similar to that existing in the Northeast USA and Canada and, therefore, the results can explain the problems of blush and bloom in these areas. Corrosion surveys by automotive companies and trim producers in these areas have shown that blush and bloom and pitting have become increasingly more severe over the last ten years.5 These problems have led to a shift away from anodized aluminum as an automotive trim material in recent years. 

An accelerated MIST test procedure has been developed which duplicates the mechanisms of corrosion of anodized aluminum trim in automotive environments. Blush and bloom of anodized aluminum automotive trim is more severe in environments with acid precipitation and this effect can be duplicated in an acidified MIST test procedure. Pitting of anodized aluminum is more prevelant in automotive environments with high chloride concentrations and this effect can be duplicated in a neutral chloride MIST test procedure. A change in the mechanism of corrosion of anodized aluminum trim from pitting to blush and bloom in chloride containing environments occurs in the pH range of 2 to 4. These results indicate that blush and bloom of anodized aluminum will become more severe as the acidity of precipitation increases. Thus more expensive trim materials such as bimetal are being used by the automotive industry. 

Corrosion of Metals and Alloys— Atmospheric Corrosion Testing—General Requirements Anodized Aluminum and Aluminum Alloys— Rating System for Evaluation of Pitting Corrosion Grid Method... 

Fig. 24. Acidic corrosion resistance of two test coupons of anodized aluminum. On the left, anodized aluminum does not show any acidic corrosion in two hours and on the right, anodized aluminum shows severe acidic corrosion after only 10 minutes immersion in the acid.

The HCl bubble test can be processed at any position of etching chamber before and after etching process. In Fig. 25, one process chamber is studied on its corrosion resistance in 5.0wt% HCl solution [76]. This method has received a wide application for the corrosion resistance study of anodized aluminum. 

A systematic study of anodized aluminum made of A16061-T6 11" thick block was carried out. It is obvious that HQ bubble test can be studied at different thickness positions to compare the differences of corrosion resistance [77]. The detail positions of different tests are shown in Fig. 26. Eleven different test methods are applied to the study. 

Figure 2. A schematic diagram of experimental cell used for corrosion tests of anode materials 1- Anode rod 2- Graphite crucible 3- Anode sample 4- Aluminum metal 5- Gas inlet ...

The impedance test for anodized aluminum (ASTM B 457) is used to study the seal performance of anodized aluminum. In this sense, the test is similar to the FACT test, except that this method uses a 1 V root mean square 1 kHz signal source from an impedance bridge to determine the sealed anodized aluminum impedance. The test area is again defined with a portable cell, and a platinum or stainless steel auxiliary electrode is typically used. The sample is immersed in 3.5% NaCl. The impedance is determined in ohms X 10. In contrast to the methods discussed previously, this test is essentially nondestructive and does not accelerate the corrosion process. 

Roberge, P. R., and Halhop, E., An Alternate Electrochemical Procedure for the Testing of Anodized Aluminum, in Haynes, G. S., and Tellefsen, K. (eds.). Cyclic Cabinet Corrosion Testing, STP 1238, Philadelphia, American Society for Testing and Materials, 1995, pp. 49-58. 

An accelerated corrosion test for some electrodeposits for anodic coatings on aluminum. Corrodkote test... 

Most often, it is the anodic polarization behavior that is useful in understanding alloy systems in various environments. Anodic polarization tests can be conducted with relatively simple equipment and the scans themselves can be done in a short period of time. They are extremely useful in studying the active-passive behavior that many materials exhibit. As the name suggests, these materials can exhibit both a highly corrosion-resistant behavior or that of a material that corrodes actively, while in the same corrodent. Metals that commonly exhibit this type of behavior include iron, titanium, aluminum, chromium, and nickel. Alloys of these materials are also subject to this type of behavior. 

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