Materials Performance is the world's most widely circulated magazine dedicated to corrosion prevention and control. MP provides information about the latest corrosion control technologies and practical applications for every industry and environment.
MATERIALS SELECTION & DESIGN FIGURE 2
(Figure 1). The same case occurred in the winter season (December to February), where the corrosion rate was <10 to 230 mg•m2
/y. The corrosion rate in Guaymas City
was lower compared with Ensenada, where corrosion occurred in six months. This indicates that in Guaymas, there was better control of climate and pollution factors indoors.
Deterioration of Steel Cans
Ranges of RH and temperature were higher than 80% and 35 ºC during the year in Ensenada, with a minimum of 35% and 25 ºC in the periods of hot winds. Levels of humidity and temperature higher than 75% and 35 °C accelerated the cor- rosion rate. In the summer, the corrosion rate was higher after one year. For tem- peratures in the range of 25 to 35 °C, and RH levels of 35 to 75%, the corrosion rate was very high. Furthermore, in the winter, at temperatures ~10 to 20 ºC and RH levels from 25 to 85%, water condenses on the metal surface and the corrosion rate increases very quickly (Table 2).
SEM and AES Analyses Figure 2(a) shows SEM images of the
sample at 500 µm (points 1 and 2), Figure 2(b) is at 5 µm (from point 1, which is represented by points A and B), and the AES spectra is shown in 2(c) after an ex- posure of 18 months. Figure 3 shows SEM images in the
external zone, at 500 µm (points 1 and 2) in 3(a), at 5 µm (from point 2, which is indicated by points A and B) in 2(b), rep- ZM[MV\QVO JZWSMV ÅTU
K [PW_[ \PM )-; spectra at 18 months of exposure indoors.
Chemical Composition Evaluation
The AES analysis represents the
chemical elements, which react with the UM\ITTQK []ZNIKM ?PMZM \PM ÅTU VW\ _I[ formed very well, it broke. Table 3 shows
NACE International, Vol. 51, No. 4
Internal evaluation of atmospheric corrosion in tin-plated steel cans: (a) SEM at 500X original magnification, (b) SEM at 5X original magnification at point 1, and (c) AES analysis of SEM 5X exposed at 18 months.
TABLE 3
Atomic concentration of steel cans (2010) Internal Zone
Elements C
Cl Fe O S
Sn
Point A (%)
14 9
20 25 20 10
Point B (%)
12 21 19 23 15 10
the atomic concentration (%) of the chemical elements in each spectrum.
Conclusions The major corrosion occurred in tin
plate steel cans and the minor in steel cans
Elements C
Cl Fe O S
Sn External Zone
Point 1 (%)
13 22 20 15 17 13
Point 2 (%)
15 10 21 24 18 12
with plastic coatings, indicating that the material without the tinned process is better to preserve sardine and tuna in good condition. SEM microphotographs show the corrosion products in Ensenada with the light stains of chlorides and the
April 2012 MATERIALS PERFORMANCE 55