Chalking and Fading on Steel Cladding

Chalking and fading coatings on steel roofing and cladding may seem harmless. Yes, it looks unsightly but at least the paint is intact, right? Well that’s where you’d be wrong.

Chalking, also referred to as “powdering” and fading paint is the start of a bigger problem, if left unchecked. Protective coatings principally consist of paint pigments encapsulate in a resin binder. This holds the coating system together and acts as an adhesive to the metal substrate.

Many business owners might say, “oh its alright, we can hold off getting that fixed for now, we’ve got more important things to worry about right now”. These are the famous last words of many who have fallen fowl of a failing coating system. Once the resin that holds everything together in paint starts to breakdown it triggers a chain reaction.

Most common causes of chalking and fading;

  • UV (ultra violet) light
  • Acid rain
  • Salt spray
  • Pollution
  • Airborne particulates abrasion

chalking fading paint diagram info graphic
Stages of chalking and fading in a paint system, from how it forms to the consequences of allowing it to develop.

What is chalking?

Chalking is a powdery residue that forms on the top layer of a protective coating. Resin binding elements in the paint degrade and separate from the pigment in the coating system. The result is a light coloured layer of lose particles. Its mostly caused by sunlight, salt spray and acid rain.

It can be wiped clean and to reveal slightly faded paint beneath. Chalking is basically the remains of damaged paint. The longer its left, the worse it gets. Paint degradation accelerates as the layers exposed to the sun become more defused. More UV light is absorbed and the paint continues to break down and fall apart.

Eventually and in extreme circumstances, adhesion of the coating to the metal substrate is lost. The roof structure is now compromised and corrosion will start to spread.

chalking paint steel roof sheet
Chalking and fading paint is a result of binder/resin breakdown.

What is fading?

Fading occurs in the pigment of the paint. UV damage also plays a part in addition to exposure to acid rain, pollution and atmospheric conditions. Resin in the coating breaks down and the colour of the paint changes, usually turning lighter.

Areas affect

Coatings exposed to sunlight are the worst affected areas. Commercial buildings such as warehouses, superstores, offices and factories along with schools, sports complexes and community centres all suffer from the elements. Structures with south and south westerly facing facades are worst affected. The sun and prevailing weather is most intense facing this direction.

steel substrate corrosion failed coating
Roof sheets suffering from corrosion due to degraded paint.

Chalking and fading paint on steel roofing is more often overlooked. When it occurs on wall cladding, its unpleasant appearance usually prompts building owners to act fast. However, a failed roof coating can have much more serious consequences. The protective paint will erode over time, exposing the substrate resulting in loss of protection. Corrosion will become rampant and the roof will eventually become untreatable, requiring complete replacement.

Why does chalking and fading happen?

Paint chalking is caused by UV (ultra violet) light from the sun. Chalking is the pigment in the paint released by the binder. When exposed to sunlight, it develops slowly over time and is a natural reaction. Chalking and fading occurs more on flat paints with a more matt finish. White or very light-coloured paints containing high levels of titanium dioxide and extenders are worst affected.

chalking paint cracked flaked
Chalking and flaking paint on cladding is unsightly.

How to treat chalking and fading?

Power washing and scrubbing with a stiff bristle brush is carried out first. Lose flaking paint is removed and the surface is ready for treatment. A base coat followed by a finishing top coating should be used. We recommend a reputable brand such as Girosil, Rooflock or AkzoNobel.

How to prevent chalking and fading?

Choose high quality coating systems that are durable designed to last longer. A reputable coating contractor, such as ourselves, should also be hired to carry out the work professionally. When a contractor who is approved by a paint manufacturer is hired a guarantee of up to 25 years will be issued for the coating system.

steel cladding faded corroded
Cladding with faded paint that has begun to detach from the substrate allowing corrosion to occur.


Chalking and fading paint is a common problem. It happens to all coatings eventually. Choosing good quality longer lasting paint applied by a professional, although more expensive initially, will save you money over time. Cheap paint applied by inexperienced individuals won’t last. Regular inspections, yearly at least, to monitor your coatings will ensure you don’t get caught out. The longer a problem with a protective coating is left, the more expensive it will be to put right.

Further reading;

Fading and chalking paint
Paint Pigment
Ultraviolet Light Radiation

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