Oilfield sucker rods are protected by the Black JAC line of coatings -- particularly Black JAC Plus and Black JAC Supreme -- which significantly outperform any product on the market.

On the right:

Top picture -- ASTM B117 Test in which oilfield sucker rods were exposed to 5% salt fog at 110°F for 192 hours. Breakdown of coating and excessive corrosion is clearly visible.
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Bottom picture -- Sucker rod subjected to same test, but treated with Black JAC Supreme. Note lack of corrosion.