Powder Coating

1.0 Scope

This specification defines the corrosion protection class options and surface finish options. It also provides guidance on the inspection of the surface finish of powder coated parts. It gives an introduction and guidance on the assessment of significant surfaces with respect to surface defects in the coating system. Unless otherwise specified we would require any powder coated parts to meet Corrosion Class C3 (Fractory C level), with a General Appearance Class B finish.

2.0 Classifications

2.1 Corrosion Protection Class

The table below defines the corrosion protection class required for various environmental conditions as described in ISO 12944-2. The powder coating application process will differ depending on which protection class is required. Unless otherwise specified the required corrosion protection class will be in line with Fractory Level C as defined in the table below.

3.0 Viewing Conditions

For all viewing situations a minimum of 1.0 metre shall apply provided that further distance be allowed commensurate with the use of the product and its in-situ viewing distances. Inspection shall be conducted using the unaided eye under 500 Lux lighting conditions.

3.1 Lux

A measurement of luminous intensity from a light source. The following table represents the illumination from common sources:

Illuminance Example

50 lux Family living room80 lux

320–500 lux Office lighting

400 lux Sunrise or sunset on a clear day.

1,000 lux Overcast day; typical TV studio lighting

10,000–25,000 lux Full daylight (not direct sun)

32,000–130,000 lux Direct sunlight

4.0 Powder Coating Defects

This specification defines powder coating defects and visual identification. Understanding these defects helps ensure high-quality finishes and helps to align expectations between different parties. Understandably the manufacturing partner, who provides coating, does not always perform metalworking processes such as laser cutting, bending or machining - however, it remains the powder coating partner's responsibility to notify Fractory if the parts received are in a condition that prevents a defect-free result. 

4.1 Definition of powder coating defects

4.1.1 Scratches

Scratches in the the surface coating are often caused after the coating has taken place during handling of parts or poor storage. Please see the general Appearance chart above to understand the acceptability of scratches depending on the appearance class. 

4.1.7 Hanging Marks

Visible unpainted spots or depressions on the surface caused by the contact points of hooks or racks. These occur where the hanging tool shielded the part from the powder spray or prevented the coating from flowing together during the curing process. Please see below examples of acceptable and Non acceptable hanging marks for a standard Class B finish

4.1.2 Uncoated surfaces

This defect is characterized by areas on the part that remain bare and uncoated after the powder coating process. This defect can occur due to inadequate coverage during application, small features (holes) or masking errors. Unpainted surfaces can lead to localized corrosion and reduced overall protection of the part. Unpainted surfaces are not allowed, unless specified otherwise. 

4.1.3 Pinholes

This defect is characterized by small holes or voids on the surface of the coating. These are often caused by out-gassing from the substrate, contaminants in the powder or on the surface of the part. Pinhole defects are permitted only if there is no more than one (1) pinhole within an area the size of a 2-euro (1 pound) coin diameter. 

4.1.4 Runs and sags

Excess powder can cause the coating to run or sag, leading to uneven thickness and poor aesthetics. This is usually due to applying too much powder in one area.  This defect is not allowed!

4.1.5 Poor adhesion

This defect is characterized, when the powder coating does not properly adhere to the substrate, it can flake or peel off. This can be due to inadequate surface preparation, such as insufficient cleaning or improper pretreatment. This defect is not allowed!

4.1.6 Bad material surface

This is when the defect is arising from the initial condition of the material surface Issues such as rust, excessive roughness, burr and grease can lead to poor adhesion and an uneven finish. This defect is not allowed!

4.1.1 Orange Peel

This defect is characterized by a surface texture that resembles the skin of an orange. It can result from incorrect application techniques, improper curing temperatures or issues with the powder material itself. Orange peel is not allowed, unless this kind of visual appearance is intentional.

5.0 Masking

To ensure specific functional areas—such as threaded holes, mating surfaces, and electrical ground points—remain free of powder coating to maintain mechanical tolerances and conductivity. Masking requirement must be defined by Fractory - if something is unclear or input information not sufficient, please ask!