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TO 1-1-700 - Robins Air Force Base

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<strong>TO</strong> 1-1-<strong>700</strong><br />

Figure 3-22. Failed Chromium Plating<br />

Table 3-1. Corrosion of Metals - Type of Attack and Appearance of Corrosion Products<br />

Alloys Type of Attack to Which Alloy Is Susceptible Appearance of Corrosion Product<br />

Magnesium Alloy Highly susceptible to pitting White, powdery, snow-like mounds, and<br />

white spots on the surface.<br />

Low Alloy Steel<br />

(4000-8000 series)<br />

Surface oxidation and pitting, surface, and intergranular<br />

Reddish-brown oxide (rust).<br />

Aluminum Alloy Surface pitting, intergranular, exfoliation, and fretting White to gray powder.<br />

Cadmium (used as a<br />

protective plating for<br />

steel)<br />

Stainless Steels<br />

(300-400 series)<br />

Nickel-base Alloy<br />

(Inconel, Monel)<br />

Copper-base Alloy,<br />

Brass, Bronze<br />

Chromium (plate)<br />

Silver and Gold<br />

Uniform surface corrosion; used as sacrificial plating to<br />

protect steel<br />

Crevice/concentration cell corrosion; some pitting in<br />

marine environments; corrosion cracking; intergranular<br />

corrosion (300 series); surface corrosion (400 series)<br />

Generally has excellent corrosion resistance qualities;<br />

susceptible to pitting in sea water<br />

Surface and intergranular corrosion<br />

Pitting (promotes rusting of steel where pits occur in<br />

plate)<br />

Gold - none; Silver - tarnish from sulfides in air; can<br />

cause galvanic corrosion of contacting metals<br />

From white powdery deposit to brown or<br />

black mottling of the surface.<br />

Rough surface; sometimes a red, brown,<br />

or black stain.<br />

Green powdery deposit.<br />

Blue or blue-green powdery deposit<br />

(patina).<br />

No visible corrosion products; blistering<br />

of plating due to rusting of the base metal<br />

and lifting of plating.<br />

Black tarnish deposits on silver surfaces<br />

3-15

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