Pre treatment Alternatives

IMG00095-20100512-1313.jpgThe two Primary Reason’s to use powder coating are...

  1. To achieve Decorative Value
    Color, Gloss, Texture, etc...    Visual Appearance
  2. To Achieve Functional Value
    Protection from Corrosion…     Protective Value

Decorative value in powder coating comes in many varieties. There are speckled, “veins”, fluorescents, reflective and texture powders varying from an 80 grit-like sandpaper finishes to a thick textures. Powders are available in all colors and gloss levels, as well as metallic and candy (semi-transparent) colors, and crystal clears.

Protective value in powder coating begins with understanding the type of material you plan to be spraying over and knowing the proper pretreatment necessary to achieve optimal adhesion to the object.
 
Almost anything can be powder coated including metal, plastic, MDF, ceramic and glass.

With regards to metal, the objective in a protective powder coating will be to stop the corrosion cell from forming. There are four conditions that must be present for corrosion to occur. They are 1. A positive pole (cathode); 2. A negative pole (anode); 3. An electrical conductor (steel, aluminum, etc); 4. An electrolyte (water).

All coatings (paint, powder coat, galvanizind, etc…) are semi-permeable and will eventually fail.

Pre-treating Steel:

A single barrier of powder coat will last a long time over properly pre-treated steel, however as with all coatings, moisture will eventually get to the surface.

tutorial1.png

If the substrate is not prepared correctly, like removing the RUST, SCALE AND SOILS and any other contaminant, the coating will fail at an accelerated pace with osmotic blistering occurring.

tutorial2.png

Rust: Rust, or oxidation, occurs when oxygen comes in contact with certain metals. Over time, the oxygen combines with the metal at an atomic level, forming a new compound called an oxide and weakening the bonds of the metal itself.

Scale: Is a thin black or dark grey layer of metal left over from the steel manufacturing process. Air trapped between the scale and the steel escapes through the coating when the part is heated during the curing process of powder coating. This leaves a passage way through the coating for water to get to the metal surface faster, which will accelerate the corrosion of the metal.

Soil: Any Material that is unwanted or which will interfere with the following process, resulting in lower than expected quality and appearance.

- Oils and lube; dirt and dust; rust preventatives; fingerprints / skin oils; hydraulic fluids; coolants; adhesives and sealants; welding by-products

And much more!

Steel is cleaned with an iron phosphate spray which is an excellent pre-treatment for steel due to its bond promoting chemical conversion characteristics.

tutorial3.png

Steel, which has rust or scale, is cleaned by abrasive blasting the contaminants off.
This leaves a profile on the metal and may require two coats of powder to properly cover the surface.

tutorial4.png

A zinc primer coating over steel is an excellent adhesion promoter and also works as a sacrificial coating once water breaks through the first barrier coating.

It is ideal to have a zinc rich primer powder coat applied to a blasted surface to properly cover the profile on the metal and to act as a sacrificial coating.

Aluminum can be pre-treated with an iron phosphate, which cleans, or chromate conversion which cleans and promotes adhesion. During this process, a thin film is produced on the aluminum surface which greatly enhances the product's ability to form a bond with the aluminum.
 
There are many other factors to be addressed to be sure the coating will last, such as controlling the chemical and ph levels well, controlling impingement times, ensuring the oven is clean, being on top of the time and temperature of the curing cycle etc… However once any substrate is pre-treated properly, you are 80% of the way to achieving an exceptionally adhered powder coat or paint.

CONTACT US TODAY

CONTACT

2121 Paramount Crescent
Abbotsford, British Columbia
Canada V2T 6A5
Tel: 604-850-2464
Fax: 604-850-2498
info@valleypowdercoat.com

All Contents Copyright © 2011 Valley Powdercoat LTD