When not to polish
Regular polishing is a critical part of maintaining an aircraft`s finish over time. Although, each aircraft is a unique case. Most of the time W&W is able to transform aircraft surfaces to a like-new condition. Unfortunately, some surfaces are just too far gone to reach a satisfactory result.
We begin each assessment by first visually inspecting the painted surface. Aircraft have some specific paint defects not found on other substrates. On most surfaces one may notice flaking, cracking, pitting & corrosion at various levels. Corrosion & pitting have little effect on the polishing process and should be brought to the attention of your A&P, I&A. Chronic flaking & crackling are not uncommon on most aircraft but appear at vastly different levels.
Flaking can be limited to nacelles, cowls & ailerons or spread across the whole aircraft. In average cases flakes come off in thin slivers, close to the width of full border. This issue usually presents no difficultly if restricted, but if the whole paint surface is compromised, a full respray is required. In rare cases, the symptoms can be quite extreme with flakes leaving the surface in finger-nail sized portions. These rare occurrences usually result from a failure in surface preparation before painting, zinc chromate, paint type, working environment and severe corrosion.
Cracking paint usually occurs from two completely different situations, both equally detrimental. The most common arises from years of abuse which only leaves a very thin layer covering the metal surface. When combined with the constant surface vibration in flight along with prolonged summer heat, the paint slowly forms small fissures. These fissures do not contain themselves but quickly spread throughout the entire painted surface. The recommended action is of course a re-spray but in certain cases we will apply protection in such areas if the owner budget demands.
The more common case we come across is a very narrow window of paint depth. Most neglected aircraft have a dull, chalky layer of paint decay covering the surface. This chalky layer certainly is oxidized paint but it can have a protective effect for the layers underneath. It is best for an oxidized layer to never appear by applying adequate protection, but human nature often hinders proper care. If the oxidized layer is removed from vigorous washing and no protection is added a viscous cycle of destruction begins. With each aggressive washing & oxidation cycle the layers of paint diminish greatly until nothing else remains over the aluminum. If your aircraft is oxidized, we do not recommend taking any action to remove the dead layer unless it will be polished & protected appropriately.
Another problem arises in other aircraft we have corrected with a similar scenario. When most owners/pilots notice an oxidized surface they quickly run to an aggressive soap & brush to remove the unsightly blemishes. However, as discussed in the aircraft cleaning care article, such chemicals do much more harm than good. These almost always leads to regular, but aggressive washing which also erodes the painted surface but leaves less visual impact. Eventually, over a decade or so the pilot/owner will notice the paint is quite dull but not chalky to the touch. This situation is the most difficult to correct. It requires days, if not weeks of polishing to safely remove the unsightly haze.
These cases can sometimes present a problem for paint correction. W & W will apply the same level of paint correction across the whole aircraft but will not compromise the paint integrity for visual appeal. Some extreme cases we have corrected will have dull areas remaining above windows, raised edges & top of the fuselage. Though such areas could easily be brought to a high shine, it goes against ethical business practices to compromise such an expensive investment. Therefore, we will polish such areas safely & protect them regardless of condition.