(9) Rust Staining. Red and yellow oxides produced from ferrous metals show as rust stains
on what appears to be a reasonable paint surface. In fact they indicate that small fissures
have developed and the metal substrate has begun to corrode. This fault should be cleaned
down to the substrate.
(10) Flaking or Peeling. This fault is the most easily confused condition. Paint is caused to
flake by numerous conditions, some of which are avoidable mistakes in application or
pretreatment, and not, as commonly thought, by deterioration in the paint film. In all cases
where the paint film adhesion has deteriorated so that the paint is lifting and flaking, the
extent of the damage and the general condition of the entire component must be considered
before a repair decision is made. If the damage is very localized, the affected area only
should be repaired in the form of patch painting. But in the event of a general deterioration,
for example upwards of 10% in patches of the total surface area, localized repair would be
false economy and a complete re-treatment should be authorized.
(11) Fig 5.10 shows the underside of a paint flake contaminated with rust, oil and chalk.
(12) Fig 5.11 shows a flaking paint system caused by the omission of primer pretreatment.
(13) Fig 5.12 shows a badly flaking paint system that requires cleaning to a suitable
substrate and renewal of the paint system. This illustration is a direct extension of Fig 5.9
where the paint was blistered.
Fig 5.10 Paint Flake
Change 1 5-9