Salt Mist Test — RTCA DO-160 Part 14 · Paint and Coating Testing

What Is Salt Spray?

This test is carried out within the scope of Chapter 14 (“Salt Fog”) of the RTCA DO-160 “Environmental Conditions and Test Procedures for Airborne Equipment” standard to evaluate the corrosion resistance of the equipment in a salty atmosphere. DO-160 is the exact same text as EUROCAE ED-14 and is recognized by ISO as ISO 7137.

Purpose of Salt Spray

The aim is to certify that aviation equipment meets the requirements for assessing the corrosion resistance of the equipment in a saline atmosphere under flight and ground conditions and to complete the equipment qualification.

Which Products Is Salt Spray Applied To?

Avionics units and displays
In-flight electronic equipment
Communication and navigation devices
Cabin and cargo compartment equipment
Sensors and actuators

In Which Sectors Is Salt Spray Used?

AutomotiveMetalConstructionMachinery

Standards Related to Salt Spray

RTCA DO-160Environmental conditions and test methods in aviation equipment test
EUROCAE ED-14
ISO 7137

Salt Spray Conditions

Kategoriler: S (standard), T (severe)
Solution: NaCl concentration defined in the standard
Cycle: Salt fog and drying stages
Time: Defined by category

Equipment for Salt Spray

Salt fog chamber
pH and solution control
Insulation resistance measuring instrument
Function monitoring

Sample Requirements for Salt Spray

Category must be defined
Initial insulation resistance should be measured
Connectors must be in the assembled state

Duration of Salt Spray

It depends on the category; typically a few days to two weeks.

Salt Spray Procedure

1Category and solution are prepared.
2The specimen is placed in the chamber.
3Salt mist and drying cycles are applied.
4The sample is washed and dried.
5Function, insulation and corrosion are evaluated.

Salt Spray Acceptance Criteria

Acceptance criteria are continued function and absence of structural corrosion.

Evaluation of Results

Corrosion at electrical connection points is particularly evaluated.

Salt Spray Report

Applied standard, revision and Part 14
Selected equipment category and justification
Applied conditions and measurement results
Function monitoring method and observations
Environmental Qualification Form (DO-160 Environmental Qualification Form) entry

Accreditation

EUROLAB holds internationally recognised accreditation obtained from accreditation bodies party to the IAF and ILAC multilateral recognition arrangements, under ISO/IEC 17025 for laboratory testing, ISO/IEC 17020 for inspection and surveillance, and ISO/IEC 17021-1 and ISO/IEC 17065 for system and product certification. This chain ensures the reports and certificates issued are accepted worldwide.

Whether this test can be offered within accredited scope depends on your product and the standard applied; since accreditation is method-based, the scope is confirmed in writing at the quotation stage.

Scope and authorisations

Related Regulations

Aviation equipment qualification requirements
EASA/FAA certification principles

Paint and Coating Testing — What Does This Testing Field Cover?

The section below describes the field that the Salt Spray test belongs to; the conditions and acceptance criteria of this particular test are given in the sections above. The scope specific to your product is confirmed in writing at the quotation stage.

Paint and coating testing measures the adhesion of a coating to the surface, its mechanical durability and its resistance to environmental effects. Because a coating is a thin layer, the results depend both on the material and on the QUALITY OF APPLICATION; the same paint gives an entirely different result over a different surface preparation.

This dual dependence is the most important knowledge in the field. A coating failure usually arises not from the paint itself but from the surface preparation: oil residue, insufficient roughening, an oxide layer or moisture. Coating tests therefore assess not only the product but also the process, and the results are used for process control.

COATING THICKNESS is a recurring variable in the field. Many durability results relate directly to thickness; a thin area becomes the starting point of corrosion. Thickness measurement is therefore reported routinely alongside the other tests and is usually taken at several points — thickness falls at edges and corners, especially on complex geometries.

Three approaches are used on the adhesion side, each giving different information. The tape test is fast and suitable for field use but is a coarse scale. The cross-cut test shows behaviour at the intersections of layers. The pull-off method produces a numerical strength value and is the most suitable for comparison.

On the mechanical side, flexibility (mandrel bending), impact resistance, hardness, abrasion and stone chip resistance are measured. Stone chipping has a special place in automotive: gravel striking the coating under real road conditions is simulated, and the result is assessed according to whether the coating continues to protect the base metal.

On the appearance side, gloss and colour difference are monitored NUMERICALLY. Colour is assessed with a colour measuring instrument rather than by eye and the colour difference is expressed as a number; this makes it possible to compare different lots and different suppliers.

On the durability side, accelerated ageing (xenon arc, fluorescent UV), humidity, condensation and salt spray are applied. The result is assessed with scales for blistering, rusting, creep from a scribe and loss of adhesion; these scales are defined in separate standards and the report must state which was used.

In industrial processes such as powder coating and electrophoretic coating, the curing cycle (temperature and time) is what determines the result. An under-cured coating looks good but has poor chemical resistance and adhesion; oven profile measurement is therefore part of coating quality control.

Method groups in this field

Thickness
Dry film thickness by magnetic and non-magnetic methods; multi-point measurement and assessment of the distribution.
Adhesion
Tape test, cross-cut test and pull-off adhesion strength.
Mechanical strength
Mandrel bend flexibility, rapid deformation (impact), pencil and scratch hardness, Taber abrasion, stone chipping.
Appearance
Gloss measurement, colour difference calculation, orange peel and surface defect assessment.
Environmental durability
Salt spray, humidity, condensation, xenon arc and fluorescent UV ageing, chemical and stain resistance.
Assessment scales
Scales for blistering, degree of rusting, creep from a scribe and loss of adhesion.

Commonly confused in this field

A coating result depends on the surface preparation; even if the paint itself is good, a poor preparation gives a poor result.
A durability result without a reported thickness cannot be compared.
The tape test is a coarse scale; numerical comparison requires the pull-off method.
Colour cannot be assessed by eye; numerical colour difference measurement is required.
An ageing result without a stated assessment scale cannot be interpreted.
If the curing cycle is incomplete the coating looks good but its durability is poor; the oven profile is part of quality control.

Which decisions these results support

Paint system approval and supplier selection
Process control of the paint line and lot acceptance
Supporting outdoor and automotive durability claims
Detecting defects arising from surface preparation
Monitoring colour and gloss consistency lot by lot

Related Tests

Frequently Asked Questions About Salt Spray

How is the equipment category determined?

The category is selected based on the equipment's mounting location on the aircraft (pressurized/non-pressurized, heated/unheated area) and aircraft type. Category selection directly determines the test conditions and is declared in the qualification form.

Is there any difference between DO-160 and ED-14?

No. RTCA DO-160 and EUROCAE ED-14 are exactly the same text; the two are considered equivalent.