Skip and Container Paints
Skip Paint is a specific form of metal paint
initially developed as a one coat direct to metal primer and finish combined for, no surprise, skips!
However, the chief characteristics of a good quality skip paint were quickly taken up by other applications and applicators looking for the same characteristics for a whole range of metal paint applications. In general, a good quality skip paint fulfils the requirements of being a single pack, solvent based direct to metal paint.
Coverage is typically in one single coat of 75 microns dry film thickness and easy to overcoat and recoat with minimal surface preparation.
The coating fulfils the role of a primer and finish in a single application so these are usually semi-gloss or gloss in a limited range of colours, originally focussed on the popular skip colours, yellow in particular was very popular until recently. These skip paints also had to have extremely good mechanical properties, usually chip resistance and corrosion resistance to ensure that if the coating was damaged the corrosion did not spread out from the dings, dents and scrapes that are common on skips.
This is achieved on a good quality skip paint by using a very short oil length alkyd resin, usually replacing pentaerythritol with glycerine as the esterifying alcohol and a
high quality non-toxic anticorrosive pigment such as Nanoguard ACP DCP or similar to avoid any issues of potential contamination of the contents of the skip with heavy metals or environmentally hazardous material
- something which has become more of a concern in recent years, prior to that it was typical to use a carcinogenic zinc chromate or derivative or zinc phosphate.
A Fast Drying Metal Paint
The use of a very short oil alkyd (typically 26 – 27 oil length) gave the formulator of the skip paint a number of advantages without having to resort to more costly chain stopped or modified alternatives which then caused problems with overcoating whilst still providing good chemical and mechanical properties. Skip paint is commonly formulated to be quick drying to give fast return to service times, sometimes as little as 2 hours for more demanding applications and this can be achieved using this combination of alkyd technology and anti-corrosive pigment. A good skip paint can also be “touched in” by brush to repair localised damage with minimal preparation, i.e. no need for blast cleaning or similar and with good adhesion properties both to the metal it is protecting and previous coats of paint (and in some cases…who knows!) leaving the painted skip as good as new and the new coat of skip paint blending in well with the old skip paint.
Some Advice on Correct Usage
There is often a temptation with skip paints to “overthin” and to reduce film thickness to economise on paint usage. However, numerous studies have shown that film thickness less than 75 microns -even with a good quality anticorrosive pigment leads to premature failure. This can indeed be caused by over thinning and by light application. This “false economy” is then usually hidden behind because the skip paint is seen as the cost rather than the cost of repainting or repair. Likewise there can be a temptation to buy in a cheaper product – there are often missing a key ingredient (usually the anti-corrosive or it is replaced with a more harmful one such as zinc chromate to give a brighter yellow without thinking of the potential consequences for the applicator and the skip operator) or have so little as to be ineffective, especially if combined with inadequate film thickness.
Skip Paints must always be applied in accordance with the technical data sheet from the supplier. This will avoid premature failure of the skip paint and ensure optimum coverage with minimal wastage.
For the best results buying a specially formulated Skip Paint which has some surface tolerance and easy overcoating with a nontoxic anticorrosive pigment such as Nanoguard ACP will also improve both your life cycle costs and environmental credentials so it is no great surprise that these skip paints are now finding favour with applicators in other direct to metal applications where the metal has to be repainted periodically to stay fresh and where heavy metal contamination can lead to other problems after painting with environmental or health and safety audits by the applicator, the skip operator and of the course the end user. The right Skip Paint always pays for itself on longer life, easier maintenance and fewer EHS concerns.