>4), with some increasing dullness in the coating appearance for test coupons O, P, and R. After 1 hour, further increasing dullness in the coating appearance for test coupons O, P, and R was observed, while all other test coupons remained relatively high in luster.

After 51 hours, variation in the coating appearance between different test coupons was observed. For instance, within the first group (BAT), test coupons AC, AD, P, and R exhibited a relatively dull coating appearance, while test coupons U, and V maintained a relatively high luster. Within the second group (AL-T), test coupons AB, and O exhibited a relatively dull coating appearance, while test coupon T maintained a relatively high luster. Within the third group (as-coated), test coupons J and K exhibited a relatively dull coating appearance, while test coupons L and M maintained a relatively high luster.

FIG. 5 shows the results of testing at a temperature of 1050 F at various times. Test coupons on the left side of the page correspond to 50 hours, while test coupons on the right side of the page correspond to 280 hours. Test coupons in the middle of the page correspond to 150 hours. Test coupons of the first group (BAT) are identified by a rounded rectangle. Test coupons of the second group (AL-T) are identified by a squared rectangle. Test coupons of the third group (as-coated) are arranged in the top row of each image.

As can be seen, the coating appearance for all test coupons remained relatively high in luster after 50 hours of being subjected to a temperature of 1050° F. After 150 hours, all test coupons remained relatively high in luster. After 280 hours, many test coupons exhibited signs of a dulling coating appearance. Specifically, within the first group (BAT), all test coupons exhibited some dulling of the coating appearance. Additionally, test coupon AC exhibited some localized areas of relatively high dulling of the coating appearance. Within the second group (AL-T), all test coupons also exhibited some dulling of the coating appearance. Additionally, test coupon AB exhibited some localized areas of relatively high dulling of the coating appearance. Within the third group (as-coated), test coupons J and K began to exhibit some dulling of their respective coating appearances. This dulling was relatively high in some localized areas and relatively low in other localized areas. Meanwhile, test coupons L and M maintained at least some luster in their respective coating appearance, while also showing some signs of dulling in comparison to treatment times of 50 and 150 hours.

Example 2

After testing described above in Example 1 was performed, efforts were made to develop more quantitative metrics on alloying resistance. In particular, test coupons were subjected to X-ray fluorescence (XRF) to quantify the aluminum-iron ratio present in the coating of certain test coupons. Scatter plots were then prepared of the XRF test results. The particular XRF program used was a proprietary program developed to generate data based on fluoresced X-ray peaks for the particular element(s) of interest. In this program, background X-ray counts were subtracted to report the X-ray counts for the specific element(s) of interest in counts per second. The results were compared to a reference (e.g., as-received samples). Because the particular program used was comparative in nature, it should be understood that in other examples, other XRF programs may be used where test XRF data is compared to a reference.

XRF testing was performed on several groups of test coupons. In particular, in a first XRF test, raw test coupons were tested to establish a baseline aluminum-iron ratio. “Raw” used in this context refers to test coupons subjected to no additional thermal cycles such as the 1200, 1150, 1100, and 1050° F. thermal cycles described above in Example 1.

Further XRF testing was performed on test coupons of the first group and the second group referred to above in Example 1. As discussed above, test coupons of the first group (BAT) were identified by a rounded rectangle and test coupons of the second group (AL-T) were identified by a squared rectangle. The results of the XRF testing performed are shown below in Table 3.

TABLE 3

Results: XRF Testing

Al/Fe
Al/Fe
Al/Fe

Al/Fe
Al/Fe
Al/Fe
Al/Fe
1050 F./
1100 F./
1100 F./

As
1050 F./
1100 F./
1100 F./
100 hr
0.5 hr
1 hr

S/C No.
Rec'd
100 hr
0.5 hr
1 hr
Percentage vs to As Received

733924-1B
3.19
3.2
2.45
2.85
100%
77%
89%

733924-1B
2.73
2.76
2.62
2.81
101%
96%
103%

733924-1B
3.19
3.33
2.84
2.43
104%
89%
76%

733924-1B
3.05
3.06
2.82
2.64
100%
93%
87%

101%