I am retired, now. My employer used to have components power coated. In 100% of the cases the powder coating failed where it was exposed to harsh road conditions. It was not the coating that failed, but the lack of proper preparation before the parts were coated. Powder coating is not paint. It is microscopic particles of plastic powder that adheres to a surface by electrostatic attraction.
https://www.quora.com/What-is-electrostatic-attractionWhen these plastic particles are heated, they melt together and form a sealed surface coating, not unlike a plastic bag.
If the surface preparation is not done correctly and if any oxidation is left in any pitting the plastic coating will fail as the hidden oxidation will continue and eventually lift the coating. My experience with powder coating was a fail because of poor preparation. The other part of the failure may have been failing to protect the coating from road-rash damage. When the coating was damaged, contaminated road water, aka electrolyte, was allowed to get behind the coating where it became trapped. The damage from corrosion was much faster. 5/15" plate that held a bunch of hydraulics failed in under three years.
I have used powder coat primer on zinc cast parts so I could get real paint to stick. I have the coating shop heat cycle my parts 5-6 times before applying the coating. This was to promote the maximum off-gassing of the zinc and other possible metals in the castings.
If this "experiment" had failed the cost for the new parts, powder coating and paint was about $1700. So far, so good.