PWIS-Free Analysis

In the “VDMA 24364 Test for substances that impair the wetting of paint (PWIS compatibility)” standard developed by the Union of German Engineers (VDI), PWIS test requirements are explained, taking into account the intended use of a product, its intended use and classification according to product groups.

This standard makes a classification based on the intended use of a product in critical areas in terms of paint-wetting impairment substances (PWIS).

Paint wetting defects are defects in the complete and even wetting of a surface with paint. The PWIS test identifies substances that are found to impair the uniform wetting of a surface with paint.

The VDMA 24364 standard includes methods for testing products for the presence of substances that disrupt paint wetting, provides their classification, and also describes the qualification for PWIS compliance. This standard was developed to assist suppliers of paint processing companies in testing and classifying their products for paint wetting impairment substances (PWIS) compatibility.

In the PWIS-Free analysis carried out within the framework of this standard, where the product is used in a paint company and which products are in contact with paint, solvents or the surfaces to be painted are taken into account.

This standard divides the surfaces into the following zones in terms of substances that cause paint wetting disorders:

• Zone I PWIS zone of high relevance: All pre-treatment, paint application and drying areas and surfaces exposed to the environment (e.g. paint supply, compressed air supply)
• Zone II PWIS relevance middle zone: This zone is the zone within the production area where the dye is used, but is not included in Zone I.
• Zone III PWIS no relevance: This zone is within the company but outside the paint production area.

Depending on the zone defined for the product's intended application area, varying levels of severity are required in the inspection to limit or exclude contamination with paint wetting disruptors in those areas.

Sample extraction in laboratory analysis is performed by several different procedures:

• Rinsing on surfaces or in hollow areas
• Rubbing the sample (dry rubbing or with solvent)
• Blowing the sample with oil-free compressed air
• Immersion of the sample for 24 hours
• Direct application of a material (paste, powder, liquid) onto the test plate
• Degassing the sample at a certain temperature and sealing it with the test plate for one hour

A product is considered to pass analysis under the selected conditions and is marked PWIS compliant if the dyed test plate does not show any wetting defects when the dye dries.

Marking of PWIS-Free conformity according to the VDMA 24364 standard must always include the test class and the paint used (solvent or water-based).

For PWIS-Free analysis, test samples must be packaged individually to avoid cross-contamination. During collection and packaging it is necessary to ensure that the test sample is free of additional contamination, for example lubricants, grease, hand cream, cosmetics and similar contaminants.

Substances that negatively affect the wetting of paint are present everywhere in daily life, so contact with these substances occurs regularly. Therefore, special precautions must be taken to prevent contamination with substances that prevent the paint from getting wet.

Sources of substances that impair the wetting of paint in production (PWIS) are:

• Lubricants (moving parts of equipment)
• Release agents and plasticizers from plastic components used in workpieces
• Residues of drawing agents and lubricants
• Hoses and sealing compounds
• Pollution dispersed via room air technology, process air technology or compressed air system
• Transfers from other production areas
• Contaminated paint material, e.g. improper handling or storage or unsuitable additives (solvents)
• Cleaning agents, cleaning cloths, abrasives, polishing agents, adhesive tapes, gloves, work clothes

Among the numerous testing, measurement, analysis and evaluation studies provided to businesses by our organization, there are also PWIS-Free analysis services for all products and applications.