Pre-treatment and Preparation

 

Pre-treatment                                                                                                                                                                                           

Pre-treatment is the process of chemical preparation of various types of metal and aluminium prior to the application of a powder coated surface finish.  In all cases of powder coating, appropriate surface pre-treatment is vital for ensuring long lasting results. Pre-treatment is key to quality – as important to the performance of the finished powder coated product as the materials used in its construction, its design, and the conditions under which it is employed. At Powder Coating Services, it is absolutely essential that high standards of pre-treatment are maintained, to ensure a consistently high-quality end product. 

Wet Stripping

Old or conflicting pre-coated materials may be removed from an object, by wet stripping - a chemical process applied through immersion in a liquid. The alternative is sandblasting (refer below).

Powder Coating Services has both in-house facilities and partner agreements with sub-contractors to efficiently wet strip hard-to-remove powder coatings from intricate parts and shapes. Items brought in for powder coating are first sorted according to the pre-treatment processes required, and older products are often in such poor condition that sandblasting may not be suitable. The alternative is immersion tank dipping, conducted at room temperature, which applies acid surface processes to remove and neutralize corrosion as required. Waste solids and expired chemicals are removed and treated by approved sub-contractors to comply with all local authority by-laws and sound environmental protection practices.

The chemicals and processes we use in pre-treatment are compatible with most known metals*. They safely remove powder coatings from galvanized steel, aluminium, zinc, copper, brass, mild steel and stainless steel. 

* Magnesium may react to paint removal strippers and items containing that element should not be powder coated. Examples are some very expensive lightweight motorsport wheels and racing bicycles. It is recommended that these not be put through the powder coating process, but rather garnet blasted as necessary and automotive wet sprayed.

Sand Blasting

Sand blasting is the act of propelling very fine pieces of material at high-velocity to clean or etch a surface.  It is an effective way of removing oxide and rust from black or welded mild steel, and provides an excellent surface for subsequent chemical pre-treatment or as a key for powder coating.

There are four main types of blasting media used.

• Garnet is free from silica and iron particles, and would generally be used for mobile or onsite applications as it has lower dust levels than iron sand. It is sourced from India and Australia.
• Grit consists of finely crushed ball bearings, and gives steel the blast profile needed for paint to adhere to the surface. Grit cannot be used on any material that uses a magnetic force, such as alternators.
• Shot is a ball bearing-like blasting medium, comprising small particles of 0.04mm to 1.4mm. It is popular with recycling units as it can be reused 40 to 50 times. As with grit, shot cannot be used with anything that has a magnetic force.
• Iron sand is a traditional blasting medium, sourced from beaches around New Zealand. Recent studies have shown iron sand to be hazardous to operators of blasting equipment, resulting in declining use. Iron sand is relatively fine and is most commonly used when blasting car panels and glass.

 
To ensure your items get the sandblasting treatment they need, we work closely with local specialists.