Zinc shield high efficiency coating anti-corrosion failure problem!

Coating on the surface of steel substrates is a commonly used anti-corrosion measure for steel materials, and coatings can play a protective, decorative or other special function (insulation, rust, mildew, conduction, etc.

Next, we analyze the causes of anti-corrosion failure of the coating and the countermeasures for the online coatingol.

The author | Zinc Shield cold spray zinc

Insufficient adhesion of the primer

In equipment based on steel materials, the coating is generally a coating anti-corrosion design

There are two main reasons that affect the adhesion of the primer:

● The pre-coating treatment of steel substrates is not complete, mainly including oil removal, rust removal, and oxide film removal;

● The surface roughness of the steel substrate is not enough

√ Response:

▷ Strengthen the pre-coating treatment of steel substrates, and operate each process in strict accordance with the requirements of the process design;

▷ The premise of the primer attached to the substrate is that it needs to have a certain roughness, and the surface of the steel substrate can only be applied after sandblasting or sand sweeping

Improper selection of topcoat

For some steel equipment, the main application environment is the outdoor environment or the environment is relatively harsh, and unreasonable topcoat selection will lead to the failure

In the long-term ultraviolet radiation or high temperature, high humidity, high salt spray and other environmental factors, it is easy to cause conventional topcoats (such as polyurethane paint, acrylic paint and other conventional topcoats) cracking, pulverization and other phenomena, and eventually lead to anti-corrosion failure

√ Response:

Fluorocarbon coatings
with stronger weather resistance should be considered.

Fluorocarbon coatings are coatings made of fluorocarbon resin as the base material and color material
.
The chemical structure of the fluorocarbon coating binder is the most stable and firm C-F chemical bond binding, and the stability and firmness of the chemical structure make the physical properties of the fluorocarbon coating different from ordinary coatings, in addition to the mechanical properties of wear resistance, impact resistance and other excellent properties, but also has a long-term anti-fading and anti-ultraviolet rays and other excellent properties
, especially in the harsh climate and environment.

The thickness of the coating is insufficient

Due to the different environments in which the coating is used, the damage and aging effect of the coating itself are also different, in a certain corrosive environment and age, the coating should ensure the minimum thickness requirements, especially the uniformity of the manual spray thickness is guaranteed to be consistent
.

√ Response:

In the design stage of the coating process, the coating thickness should be specified according to the specific environment and service life requirements in ISO12944-2, and the coating quality
should be strictly controlled during the coating process and after the coating.

The equipment structure design is not good

In the early stage of equipment structure design, we should start to consider the anti-corrosion requirements of the overall structure, because the unreasonable design of the structure is one
of the reasons for the failure of the coating anti-corrosion.
In the connection of different positions of the equipment components, most of them use riveting, welding, screws and other connection methods, often these connections if they use different metal materials, then the potential of these metals is bound to be different, different metals contact or through other conductors connected, if in the same medium, it will cause local corrosion of different metal contact parts, that is, galvanic corrosion
.

In addition, due to the gap caused by the design defects caused by the structural design stage (some gaps in the structural design are inevitable), the primary battery is generated in the face of precipitation or moisture, and the severe corrosion
can begin in the narrow gap.

The corrosion of the coating starts from the joint of different metal materials or the gap on the structure, which starts with galvanic corrosion or crevice corrosion, and will slowly spread to the entire coating, eventually leading to the failure
of the coating anti-corrosion.

√ Response:

For galvanic corrosion, in the early stage of structural design, it is necessary to avoid gaps and potential differences in the connector as much as possible, try to select a metal with a close potential as the electric couple in contact, and should increase the insulation material between the contact metal, such as the use of insulating rubber pads, insulation glue, etc.
to insulate the heterogeneous metal, so as to block the generation
of galvanic corrosion.

For crevice corrosion, in the early stage of structural design should try to avoid the generation of gaps, for the inevitable structural design of gaps, should be after the assembly of equipment components, before painting for sealing treatment, you can use sealant and other materials, sealing treatment and then coating to prevent the generation
of crevice corrosion.

Coating control factors at different stages

There are many reasons for coating corrosion failure, and there are many types of corrosion, which need to be considered
comprehensively.

* In the structural design stage of the product, it is necessary to carry out reasonable structural design to avoid unnecessary structural defects and the selection of dissimilar metal materials that are in contact;

* In the process design stage, it is necessary to correctly select the appropriate coating according to the requirements of the environment of use and the service life and the thickness of the coating;

* In the production stage of the product, it is necessary to strictly follow the process design requirements to do a good job in each link, especially the pre-treatment of the substrate, as well as the sealing operation, and complete the coating with quality and quantity;

*In the product storage stage, the storage environment of the product should be controlled to avoid high humidity, high heat and high salt spray environment
.
In the use stage of the product, to avoid mechanical wear and fatigue fracture and other factors caused by the coating break should be avoided as much as possible;

*The most important thing is to carry out regular maintenance, timely repair of the location of corrosion spots, and avoid the anti-corrosion failure
of the coating as a whole.