Plant Cuttings

PDL stops the rot

Who'd have thought it? juice from the fruit of the date palm Phoenix dactylifera inhibits corrosion of aluminium alloy in salt water.
PDL stops the rot
PDL stops the rot

This item is not about ‘who’d’ve thought it?’, but is firmly in the ‘why would anybody think to try it out in the first place (but aren’t you glad they did!)?’ category.

Husnu Gerengi (Duzce University, Turkey) demonstrates that juice from the fruit of the date palm (Phoenix dactylifera – PDL) inhibits corrosion of aluminium alloy AA7075 in 3.5 % NaCl (the salt strength of ‘average’ seawater). The relevance of this is that the alloy is commonly used in body panels of the cooling system in cars, in hydrogen gas vessels with high-temperature applications, and in the aerospace industry (where you definitely don’t want metal bits corroding and dropping off of the aircraft – not when it’s up in the air anyway).

Although inorganic, anti-corrosion chemicals are used for aluminium alloys, they frequently contain chromates, which are highly toxic, as graphically demonstrated in the film Erin Brockovich. Safer, more environmentally benign solutions are therefore sought. Although date juice seems an unlikely thing to try, experimentation was inspired by anti-corrosion success of Hymn Rehan with leaf extract of PDL. Quite why Rehan was inspired to try out leaf extracts in this way is a mystery for another day (scrutiny of his paper doesn’t reveal the answer). Although date juice contains several sugars, Gerengi suggests that it is the glucose component that is adsorbed onto the aluminium’s surface and is the main component in the inhibitory effect.

[For more on this fascinating area of ‘green chemistry’ and corrosion-inhibition by plant extracts, why not try this review by Ambrish Singh et al. or this one by Joseph Buchweishaija? – Ed.]

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